During World War II, the U.S. Navy (USN) acquired 706 North American Aviation (NAA) B-25 Mitchell medium bombers >from the U.S. Army Air Forces (USAAF). These aircraft, designated PBJ by the USN, equipped a total of sixteen U.S. Marine Corps (USMC) bombing squadrons during the war, eight of which served in the Pacific. This article describes the various B-25 models and their use by the USMC.
The feeling of many U.S. Army Air Corps (USAAC) officers in the late 1930s was that strategic bombing was the primary mission of an air force. (NOTE: The USAAC was superseded by the USAAF on 20 June 1941.) However, the official view of the U.S. War Department, stated as late as October 1938, was that "the Infantry Division continues to be the basic combat element by which battles are won, the necessary enemy field forces destroyed, and captured territory held." In the USAAC, the attack aircraft was designed for immediate support of ground troops and since they operated at low altitude, speed was of the essence. In 1938, the six USAAC attack squadrons based in the U.S. were flying the Northrop A-17, a single-engine aircraft with a top speed of 220 mph (354 km/h) and a bomb load of 654 pounds (297 kg). To meet their obligation to provide close air support (CAS) for the infantry, the USAAC issued requirements for a new twin-engined light bomber with a range of 1,200 miles (1,930 km), the ability to carry a 1,200 pound (544 kg) bomb load and to be used exclusively in the attack mode.
NAA entered their model NA-40 in this competition. (For a brief history of NAA, see NJ, North American.) This was NAAs second multi-engined aircraft; the first was the Model NA-21 which had been entered in the 1936 competition for a high-altitude bomber. The NA-21 lost in a competition to the Douglas B-18A simply because of cost; the cost of the B-18A was almost half of the NA-21. The USAAC purchased the one and only NA-21 in 1939 designating it XB-21.
In the light bomber competition, the NAA Model NA-40 competed with the Douglas Model DB-7 which had been under development as a private venture since 1936. Again, the NAA entry lost to the Douglas Model DB-7 which was ordered by the USAAC as the A-20, designated BD, q.v.,in USN service.
On 12 January 1939, President Franklin D. Roosevelt addressed the U.S. Congress and, describing USAAC aircraft as "antiquated weapons," urged the Congress to appropriate US$300 million (US$3.7 billion in year 2000 dollars) for the purchase of new airplanes. With the influx of money, the USAAC developed requirements for another class of tactical aircraft, the medium bomber. These aircraft were intended to operate at medium altitudes of 8,000 to 14,000 feet (2,438 to 4,267 meters) to bomb depots, fortified positions, railroad yards and other targets along or behind the battle line. Having a heavier bomb load and greater range than the light bomber, the medium bomber could supplement the work of light bombers and could also assist the long-range heavy bombers against the nearer targets in a strategic bombardment effort.
The USAAC issued Air Corps Proposal Number 39-640 on 11 March 1939 for a medium bomber with a bomb load of 3,000 pounds (1,361 kg), a range of 2,000 miles (3,219 km) and a top speed over 300 mph (483 km/h). Burnelli, Consolidated, Douglas, Martin, NAA, Stearman and Vought-Sikorsky entered designs; the Martin Model 179 was the winner of the competition followed by the NAA Model NA-62 and the Douglas entry and the USAAC placed orders for all three aircraft. The Douglas entry was an improved B-18A but only 38 aircraft were built as the B-23 Dragon. The Martin Model 179 was a very advanced aircraft for the day but Martin estimated that they could only deliver 201 aircraft in the next 24-months and the USAAC ordered 201 Model 179s as B-26s, designated JM, q.v., by the USN. The desire of the USAAC to possess modern aircraft was so great that an order for 184 NAA Model NA-62s, designated B-25s, was placed on 20 September 1939; this was the first of 9,815 B-25s built during the war. When the USAAC/USAAF started approving names for aircraft, the B-25 was named Mitchell in honor of Colonel William L. "Billy" Mitchell (1879-1936), an outspoken air power advocate who was court martialed, convicted, and resigned his commission in 1926.
The standard procedure in the prewar USAAC was for the manufacturer to build and test experimental type aircraft at their own expense with no guarantees of government contracts until the aircraft was proven; the USAAC would then order two or three experimental aircraft and if these looked promising, thirteen service test aircraft would be ordered and distributed to active duty units for testing. Finally, if the service test aircraft looked promising, a production contract would follow usually two or three years after the flight of the first experimental aircraft. These procedures were abandoned with the B-23, B-25 and B-26 because of the world situation and orders were placed for both aircraft based entirely on paper projections.
The 184 aircraft ordered in 1939 were delivered as 24 B-25-NAs, 40 B-25A-NAs and 120 B-25B-NAs, all of which went into service with the USAAC/USAAF. All bore the same NAA Model number, NA-62. The 24 B-25-NAs were twin-engined, all-metal, mid-wing monoplanes with twin fins and rudders. The landing gear was a hydraulically operated tricycle type with all wheels retracting aft, the main landing gear into the underhung engine nacelles and the nose wheel and tail skid into the fuselage. Power was provided by two 1,700 hp (1,268 kW) Wright R-2600-9 fourteen-cylinder, two-row, air-cooled radial engines with two-speed superchargers. The first nine B-25-NAs had wings with constant dihedral but stability problems caused NAA to redesign the wing starting with the tenth aircraft. The resulting wing outboard of the engine nacelles had zero dihedral giving the aircraft its characteristic gull wing. Four different styles of twin fins and rudders were tried before the final version was selected. The aircraft carried a crew of five, pilot, co-pilot, bombardier, navigator/radio operator and one gunner.
The first B-25-NA was delivered in February 1941 and even for the day, the armament was very weak, three flexible, hand held 30-caliber (7.62 mm) machine guns located in the nose, waist and aft ventral position and a flexible 50-caliber (12.7 mm) machine gun in the tail. The tail gunner knelt in a glazed area; the aft end of the glazed area featured clam shell doors permitting the machine gun to be traversed. The B-25-NA was declared obsolete in 1942 and all survivors were redesignated RB-25-NAs, the R indicating restricted, i.e., non-combat, usage.
The second production version, 40 B-25A-NAs, were improved B-25-NAs designed to make the aircraft combat ready; the improvements included additional armor protection for the crew and self-sealing fuel cells. The armament remained the same as the B-25-NA. All B-25A-NAs were redesignated RB-25A-NAs in 1942.
The third production version, 120 B-25B-NAs, were improved B-25A-NAs; the improvements were in the aircraft armament. The B-25B-NA was equipped with two Bendix electrically operated turrets with two 50-caliber (12.7 mm) machine guns located aft of the bomb bay. The dorsal turret was manned while the remotely operated ventral turret, sighted with a periscope, retracted into the fuselage. There were many problems with the ventral turret; if lowered too quickly, the retracting micro switches of the turret were frequently damaged preventing the turret from retracting into the fuselage thus increasing drag and reducing speed. The turret also collected mud on unimproved airfields and because of these problems, it was frequently removed in the field. With the addition of these turrets, the 50-caliber (12.7 mm) tail gun was removed along with the armor plate in the tail.
The B-25B-NA gained fame when on 18 April 1942, Lieutenant Colonel James H. Doolittle led 16 B-25Bs from the aircraft carrier USS Hornet (CV-8) in a raid on Japan. Although the raid caused minimal damage, the boost in American morale was tremendous. All B-25B-NAs were redesignated RB-25B-NAs in 1943.
Let us digress at this point to describe how and why the USN and USMC acquired B-25s. During the interwar years, the USN had always used multi-engined seaplanes as patrol bombers; the main advantage of this type of aircraft was that airfields were nonexistent in many parts of the world and a seaplane could land on the water and be supported by a ship. The disadvantages of the seaplane were that they were slow and lacked defensive armament, range and bomb load.
One of the axioms of World War II was that as soon as territory was occupied or conquered, the winning force would build airfields for landbased aircraft to support both offensive and defensive operations. When the U.S. entered World War II, the USN realized that landbased aircraft were superior to seaplanes in antisubmarine warfare (ASW) operations and approached the USAAF with a request for Consolidated B-24 Liberators. The USAAF was reluctant to agree to sharing the production of these aircraft because of their own lack of long-range heavy bombers. However, an agreement was finally reached on 7 July 1942 whereby the USAAF would transfer a specified number of Consolidated B-24 Liberators, designated PB4Y, q.v., in USN service; B-25s; and Lockheed B-34 Venturas, designated PV, q.v., in USN service. Part of this agreement concerned two Boeing aircraft, the PBB Sea Ranger, q.v., a twin-engine seaplane, and the B-29 Superfortress.
In 1941, NAA had agreed to assemble B-29s at a new plant located at Fairfax Airport in Kansas City, Kansas after an order for 1,200 B-25Ds had been completed. At the time, the USN had placed an order with Boeing for 57 PBB-1 Sea Rangers to be built at the Boeing plant in Renton, Washington. Part of the agreement reached between the USAAF and USN in 1942 was that the PBB-1 would be cancelled allowing Boeing to build the B-29 in the Renton plant thus freeing the NAA plant in Kansas City for the production of B-25s. However, it would be February 1943 by the time the first B-25 would be available for the USN and by that time, they had begun to receive the B-24s and B-34s and they had no need for the B-25. However, the USMC was looking for a medium bomber that had a greater range than the single-engined aircraft they were using Marines agreed to take the B-25s and use them for "night heckling" missions or CAS of beachheads and landings. This was nothing new for the USMC; they were accustomed to receiving obsolete or surplus equipment from the Navy or Army.
The fourth production model, the B-25C-NA, was the first aircraft received by the USMC which designated it PBJ-1C.
Note that this designation did not follow the standard USN designation system; all B-25s in USMC service were designated
PBJ-1 followed by an alpha character which was identical to the USAAF's Series Letter, e.g., the PBJ-1C was a B-25C, the
PBJ-1H was a B-25H, etc. The 1,625 B-25Cs were ordered as follows:
The major differences between the B-25B-NA and the B-25C-NA were (1) the use of upgraded R-2600-13 engines, (2) the addition of deicer and anti-icing systems, (3) a revised tail skid, (4) strengthening of the outer wing panels, (5) a cabin heater in the left wing and (6) a revised brake system and bomb racks. Starting with the 384th B-25C-NA, the fuel capacity was increased and a navigator sighting blister was installed aft of the cockpit. Effective with the B-25C-5-NA, the single flexible 30 caliber (7.62 mm) machine gun in the nose was replaced with two 50 caliber (12.7 mm) machine guns, one fixed and one flexible. Finally, the B-25C-25-NAs featured (1) a "clear vision" windshield, (2) a 215 US gallon (814 liter) self sealing fuel cell in the bomb bay and (3) a 335 US gallon (1,268 liter) metal fuel tank in the bomb bay on every second aircraft. All of these aircraft were delivered between December 1941 and 1943.
All of the aircraft described above, B-25-NA through B-25C-NA, were built at NAA's plant at Los Angeles Municipal Airport (Mines Field), California which is now Los Angeles International Airport (LAX).
The fifth production model, the B-25D-NC, was built at the Kansas City, Kansas plant and was essentially identical to the B-25C-NA. The 2,290 aircraft were ordered as follows:
Modifications to the B-25D-NCs included (1) the addition of the navigator's scanning blister, external wing bomb racks and provision for a torpedo rack installation starting with the B-25D-1-NC; (2) replacement of the 30 caliber (7.62 mm) machine gun with two 50 caliber (12.7 mm) machine guns starting with the B-25D-5-NC; and (3) installation of a "clear vision" windshield, a 230 US gallon (871 liter) self sealing fuel cell in the bomb bay and a 325 US gallon (1,230 liter) metal fuel tank in the bomb bay on every second aircraft, and installation of armor plate behind the co-pilot on the B-25D-20-NC.
The XB-25E-NA was a B-25C-10-NA modified to test thermal deicing equipment. The program centered around the development of an engine exhaust gas to air heat exchanger to prevent the buildup of ice on the wings and tail surfaces of the aircraft. The aircraft was modified by NAA in 1943 and the XB-25E-NA continued in ice research until February 1953.
The B-25F designation was not assigned to any aircraft.
Before continuing with the descriptions of the various B-25/PBJ models, we must stop to consider the man who was responsible for changing the mission and configuration of the B-25. That man was Paul I. "Pappy" Gunn. Paul Gunn was born in Arkansas in 1900 and enlisted in the USN in 1917. In 1925, he completed flight training and became a Naval Aviation Pilot (NAP), i.e., an enlisted man rated as a pilot, and became known as a outstanding flyer. After serving 20 years in the USN, Gunn retired as a chief petty officer and moved his family to the Philippines where he became a pilot and operations manager for Philippine Airlines.
After the Japanese attack on Pearl Harbor, Philippine Airlines was absorbed by the USAAF's Far East Air Force (later Fifth Air Force) in the Philippines and Gunn, at age 41, was commissioned a captain in the U.S. Army. His first assignment was planning for the evacuation of military personnel from the Philippines to Australia; Gunn was one of the USAAF pilots who made it to Australia but his wife and four children were captured by the Japanese and were interned in the Philippines until the islands were recaptured by the U.S. in 1945.
The advantages of using light and medium bombers at low altitude in strafing missions soon became evident in the Southwest Pacific Area (SWPA). For bombing, the parafrag bomb, a 23 pound (10.4 kg) fragmentation bomb with an instantaneous fuze and a parachute attached, was developed. These bombs were released at low altitude and the parachute on the bomb permitted the aircraft to escape without being damaged by the exploding bombs. Another strategy that was tested and adopted was skip bombing which required a low-level approach and dropping a bomb so that it "skipped" across the water into the side of a ship. These low level missions were often flown against well defended targets and the bomber crew needed additional armament in the nose of the aircraft. In the fall of 1942, "Pappy" Gunn and an engineering officer at Amberly Field, Queensland, Australia modified a Douglas A-20A Havoc by installing four 50 caliber (12.7 mm) machine guns in the nose and a single 50 caliber (12.7 mm) machine gun in a blister pack on each side of the forward fuselage. The A-20 was a short range aircraft and this liability was improved by the installation of two 450 US gallon (1,703 liter) fuel tanks in the bomb bay just leaving space for parafrag bombs. These modified A-20s were very successful but the installation of the two fuel tanks in the bomb bay reduced the bomb load thus reducing the aircrafts effectiveness.
The B-25 was slower than the A-20 but had greater range so "Pappy" Gunn and Jack Fox, an NAA field service representative, began looking at modifying the fourth B-25C-NA as a strafer. The modifications consisted of (1) removing the bombardier's equipment and installing four 50 caliber (12.7 mm) machine guns with 500 rounds per gun (rpg) in the nose; (2) installing two 50 caliber (12.7 mm) machine guns in blister packs on both sides of the forward fuselage; (3) installing three Douglas A-20A fragmentation bomb racks in the right side of the bomb bay leaving the space on the left side for bombs or fuel; and (4) removing the remotely operated ventral turret. The modified B-25 strafers could carry 60 parafrag bombs together with six 100-pound (45.4 kg) general purpose (GP) bombs in the bomb bay.
The modified aircraft, now named Pappy's Folly, was flown to New Guinea for testing by an operational squadron. The crews were impressed and by the end of February 1943, 12 B-25s had been converted to strafers in Australia. The modified A-20 and B-25 strafers proved their worth during the Battle of the Bismarck Sea in March 1943 when a squadron sank four Japanese cargo ships and two destroyers in 15 minutes. As a result, the modification of B-25s into strafers went into high gear and by the end of August 1943, five squadrons were equipped with these aircraft. By the time the modification program was shut down in September 1943, 175 B-25Cs and Ds had been modified. The leaders of the USAAF's Thirteenth Air Force in the Solomon Islands were also impressed and they began modifying their B-25Cs and Ds into strafers; they were followed by the Seventh Air Force in the central Pacific, the Ninth Air Force in Egypt, and the Tenth Air Force in India and Burma which also converted B-25Cs and Ds into strafers.
"Pappy" Gunn left the USAAF in 1946 as a colonel and returned to the Philippines. For additional information about him, read "Kenney, General George C. The Saga of Pappy Gunn. New York, N.Y.: Duell, Sloan and Pearce, 1959. 133 pages."
Attempts to mount a cannon in an aircraft date back to 1910 when the Frenchman Gabriel Voisin mounted a 37 mm cannon in one of his biplanes. Work continued in the 1930s and early 1940s on an aircraft mounting a 75 mm gun but none went into production. NAA began work in early 1942 on a cannon firing B-25 and the USAAF gave them the go ahead to equip an aircraft with the 75 mm M4 cannon. With approval from the military, the last B-25C-1-NA was modified as the XB-25G-NA. The modifications consisted of replacing the greenhouse nose with a solid nose that was 26 inches (66 cm) shorter and the installation of the cannon, with 21 rounds of ammunition, and two 50 caliber (12.7 mm) machine guns in the nose. The XB-25G-NA first flew on 22 October 1942; firing of the cannon began the next day. The cannon was manually loaded by the navigator and fired by the pilot.
An order for 400 B-25Gs, which were B-25Cs with the new nose, was placed on 25 June 1942; 100 were delivered as B-25G-1-NAs, NA Model NA-93; 200 were delivered as B-25G-5-NAs, NA Model NA-96; and 100 as B-25G-10-NAs, also NA-96s. All were built at the Los Angeles plant. The remote controlled ventral turret was removed effective with the 100th B-25G-5-NA. In addition to these aircraft, the NAA modification center at Kansas City modified five B-25C-15-NAs and 58 B-25C-20 and -25s and they were redesignated B-25Gs. These aircraft were delivered between May and August 1943 with one going to the USMC as a PBJ-1G.
Sixty three of the B-25Gs were sent to the Fifth Air Force in the SWPA with the understanding that they could modify them if necessary. When they arrived, "Pappy" Gunn tested them against Japanese targets. He was pleased with the accuracy of the cannon, but he recommended that four, instead of two, 50 caliber (12.7 mm) machine guns should be installed in the nose. After 300-400 rounds of ammunition had been fired in the cannon, the ground crew found that the "skin began to ripple and tear loose at the bomb bay, the leading edge of the wing cracked between nacelles and fuselage," and the blast obviously affected the adjacent primary structure. These problems were solved by "beefing up" the structure at critical points; this required the addition of 97 separate items, 52 of them had to be fabricated locally. A total of 38 of the B-25Gs were modified in Australia and entered combat with the Fifth Air Force.
Although the B-25G was not overly successful in combat operations, the USAAF still wanted a cannon firing attack aircraft and this resulted in the seventh production version, the B-25H which featured many significant offensive and defensive changes. The 140th B-25C-10-NA was modified and became the B-25H prototype. For test purposes, the aircraft's nose armament was identical to the B-25G, i.e., the 75 mm M4 cannon and two 50 caliber (12.7 mm) machine guns. The aircraft made it maiden flight on 15 May 1943 and production of the seventh version of the B-25, all built at the Los Angeles plant, began soon thereafter. The USAAF had already placed an order for 1,000 B-25Hs, NAA Model NA-98, on 21 August 1942. These aircraft were delivered as 300 B-25H-1-NAs; 300 B-25H-5-NAs; and 400 B-25H-10-NAs. The major differences between the B-25G and B-25H were (1) the elimination of a co-pilot, (2) the replacement of the 75 mm M4 cannon with the lighter 75 mm T13E1 cannon with 21 rounds of ammunition, (3) the installation of four 50 caliber (12.7 mm) machine guns in the nose rather than two, (4) the installation of two 50 caliber (12.7 mm) machine guns in blister guns on the right side of the fuselage, (5) the dorsal turret was moved forward to the navigator's position just behind the cockpit, (6) the installation of a Bell electro-hydraulic tail turret with two 50 caliber (12.7 mm) machine guns, and (7) the installation of two staggered waist gun stations with a 50 caliber (12.7 mm) machine gun in each. Bombing and torpedo equipment remained unchanged but there were numerous changes with the radio, electrical and hydraulic equipment. Subsequent changes included (1) the installation of two 50 caliber (12.7 mm) machine guns in blisters on the left side of the fuselage effective with the 301st B-25H, and (2) removal of equipment necessary for dropping 2,000 pound (907.2 kg) bombs on the 431st B-25H.
The first B-25H-1-NA came off the assembly line on 31 July 1943 and deliveries to the USAAF began in August 1943. The USMC received 248 aircraft, 52 B-25H-5-NAs and 196 B-25H-10-NAs. The last B-25H was accepted in July 1944.
The eighth and last B-25 was the NAA Model NA-108 produced as the B-25J all of which were built at the Kansas City plant. The B-25Js, or NAA Model NA-108s, were essentially B-25Hs with (1) a greenhouse nose with one fixed and one flexible 50 caliber (12.7 mm) machine gun instead of a solid nose, (2) provisions for a co-pilot and a bombardier, (3) two 50 caliber (12.7 mm) machine guns in blister packs on both sides of the forward fuselage, and (4) omission of the cannon and four 50 caliber (12.7 mm) machine guns in the nose. This model could also carry three 1,000 pound (453.6 kg) bombs instead of two; two 1,600 pounds (725.7 kg) armor piercing bombs; and provision for six 325 pound (147.4 kg) depth charges on wing racks. A total of 4,318 B-25Js were built, in addition to 72 incomplete airframes, the most of any version. These consisted of 555 B-25J-1-NCs, 320 B-25J-5-NCs, 410 B-25J-10-NCs, 400 B-25J-15-NCs, 800 B-25-20-NCs, 1,000 B-25J-25-NCs, 800 B-25J-30-NCs, and 95 B-25J-25-NCs. Major changes in the various blocks included:
The first B-25Js were delivered between December 1943 and August 1945. The USMC received 255 aircraft, i.e., 14 B-25J-1-NCs; 7 B-25J-5-NCs; 7 B-25J-10-NCs; 20 B-25J-15-NCs; 84 B-25J-20-NCs; 47 B-25J-25-NCs; and 76 B-25J-30-NCs.
A total of 453 B-25Js were modified to eight gun strafers. These aircraft featured a solid nose with eight forward firing 50 caliber (12.7 mm) machine guns giving the aircraft the capability of firing fourteen 50 caliber (12.7 mm) machine guns forward (eight in the nose, four in the blister packs on the side of the aircraft and two in the top turret). The aircraft also had four other machine guns, two in the waist and two in the tail, that could be fired after passing over the target. A modified aircraft were one Block 17, 123 Block 22s, 78 Block 27s, 237 Block 32s and 14 Block 14s.
Production of the B-25 ceased shortly after V-J Day.
PRODUCTION HISTORY
The USMC received the following aircraft:
OPERATIONAL HISTORY
The USN accepted 188 PBJs in 1943, 395 in 1944 and 123 in 1945. These aircraft equipped 16 USMC squadrons, eight of which served in the Pacific. In 1945, four squadrons were decommissioned without having left the U.S. and four others were redesignated torpedo bomber squadrons and re-equipped with the Eastern Aircraft TBM Avengers, q.v.
The PBJ-1Cs were mainly used for training while the first Mitchell to see combat was the PBJ-1D. When operated by the Marines, the B-25s were heavily modified. Since two of their major missions were anti-shipping strikes and night heckling missions, many aircraft were equipped with radar. Initially, an AN/APS-2 airborne search radar system was installed in PBJ-1Ds; the remote ventral turret was removed and a radome installed housing the radar antenna. As with the turret, the radome was retractable. Later, the AN/APS-3 airborne search radar system with the radome mounted on the nose above the bombardiers station was installed on PBJ-1Ds; this configuration was nicknamed Hose Nose. NAA delivered versions of the PBJ-1J with the radar antenna housed in a pod on the starboard wing tip but the Marines felt that the nose mounted radar was superior because (1) it gave about 20 degrees more coverage, (2) better weight distribution and (3) ease of maintenance. Many of the PBJ-1Js received in the Pacific were modified into the Hose Nose configuration.
Armament was also an area where the PBJ-1Ds were heavily modified. Like the USAAF's Fifth and Thirteenth Air Forces, these aircraft were modified into strafers by installing four fixed 50 caliber (12.7 mm) machine guns in the nose and two 50 caliber (12.7 mm) machine guns in blisters on both sides of the forward fuselage. Another modification was the installation of 50 caliber (12.7 mm) machine guns in the small waist windows between the dorsal turret and the tail; later PBJ-1Ds were modified with the larger "bay windows" of the B-25H and J. The last major modification was the addition of a tail turret with one 50 caliber (12.7 mm) machine gun. The canopy of the tail gun was similar to that used on the B-25H and J.
The Marine PBJ squadrons served ashore as a garrison air force to attack bypassed Japanese bases and other installations. The primary operations were at night against shipping and land targets. In the South Pacific, five squadrons flew missions against Japanese installations at or near Rabaul (4.12S, 152.12E) on New Britain Island and Kavieng (2.35S, 150.50E) on the northwest coast of New Ireland Island in the Bismarck Archipelago and Bougainville Island in the British Solomon Islands. One squadron, based in the Marshall Islands, was tasked with preventing resupply of bypassed Japanese bases in those islands while one squadron was based in the Mariana Islands, and later Iwo Jima and Okinawa, flying night anti-shipping missions. The eighth squadron departed the U.S. in July 1945 and ended the war based on Midway Island.
The last Marine Mitchell, a PBJ-1J assigned to Marine Bombing Squadron Six Hundred Twelve (VMB-612) at Marine Corps Air Depot (MCAD) Miramar, San Diego, California, was removed from the inventory on 31 January 1946. A brief history of the sixteen VMBs is listed below.
The eight squadrons that saw service in the Pacific were:
VMB-413 was the first Marine PBJ squadron formed. Commissioned at Marine Corps Air Station (MCAS) Cherry Point, North Carolina on 1 March 1943 the squadron moved to Naval Air Station (NAS) North Island, San Diego, California in December 1943 after completing training. Departing the U.S. on 3 January 1944 with their PBJs tied down on the deck of the escort aircraft carrier USS Kalinin Bay (CVE-68) for transport to MCAS Ewa, Territory of Hawaii. The air echelon then flew their aircraft to Naval Operating Base (NOB) Espiritu Santo on Espiritu Santo Island, New Hebrides Islands (15.15S, 166.51E) arriving on 27 January 1944 with 13 PBJ-1Ds. After receiving familiarization training, VMB-413 moved forward to Stirling Island, Treasury Islands, British Solomon Islands (7.13S, 155.19E), on 7 March. Located about 30 miles (48 km) off the southwest coast of Bougainville Island, this base made it easy to fly bombing and heckling missions against targets on Bougainville and the huge Japanese base at Rabaul on New Britain Island. The squadron flew its first mission against a supply dump near Rabaul on 14 March and for the next week, joined USAAF and USN aircraft in attacking the Rabaul area. After these preliminary raids, VMB-413 switched to its primary function, night heckling raids against Japanese installations on Bougainville and Rabaul. The squadron returned to NOB Espiritu Santo in May 1944 for rest and recreation and then moved forward to Munda Airfield (8.00S, 157.15E) on New Georgia Island in the British Solomon Islands and commenced bombing and strafing heckling operations against the Kahili-Choiseul area of Bougainville Island. On 18 October 1944, the squadron moved to Marine Corps Air Facility (MCAF) Emirau on Emirau Island (1.40S, 150.00E) in the St. Matthias Group of the Bismarck Archipelago. For the remainder of the war, the squadron flew missions against the bypassed Japanese forces on New Britain and New Ireland Islands. On 17 August 1945, the squadron was ordered to transfer to Titcomb Field, Malabang, Mindanao, Philippines Islands.
VMB-423 was commissioned at MCAS Cherry Point on 15 September 1943. The squadron moved to MCAS Edenton, North Carolina in October 1943 and upon completion of their training, transferred to MCAS El Centro, California arriving on 3 January 1944 with their PBJ-1Ds. The ground echelon sailed for NOB Espiritu Santo in the cargo ship and aircraft ferry USS Hammondsport (AKV-2) and the escort aircraft carrier USS Prince William (CVE-31) arriving on 11 March 1944; the air echelon arrived on 10 April. After completing familiarization training, the air echelon was operating from Stirling Island by the middle of May; their first combat mission on 14 May. Meanwhile, the ground echelon had been dispatched to Naval Auxiliary Air Facility (NAAF) Green Island (4.38S, 154.15E) in the Solomon Islands, located about halfway between Buka and New Ireland, and the air echelon joined them on 21 June; by the end of June, the squadron had ten PBJ-1Ds. For the next year, the squadron carried out day and night air attacks against targets on New Britain and New Ireland Islands in the Bismarck Archipelago and suppled CAS for Australian troops on Bougainville Island. On 12 June 1945, the squadron moved to MCAF Emirau on Emirau Island where it conducted strikes against New Britain and New Ireland Islands until 10 August at which time it began a movement to Titcomb Field, Malabang, Mindanao, Philippines Islands arriving on 16 August just after the war ended.
VMB-433 was commissioned at MCAS Cherry Point on 15 September 1943. The squadron trained at Cherry Point and at Marine Corps Auxiliary Air Field (MCAAF) Camp Lejeune, North Carolina (Peters Point Field) and upon completion, moved to MCAS El Centro and continued their training syllabus. On 26 May 1944, the ground echelon departed by ship for the Solomon Islands; the next day, the air echelon departed and arrived at NAAF Green Island on 14 July for temporary duty; this temporary duty consisted of flying with VMB-413 and VMB-423 to gain combat experience. In August 1944, the air and ground echelons were reunited at NOB Espiritu Santo where the squadron remained for the remainder of the war. On 16 August 1945, the squadron was ordered to Titcomb Field, Malabang, Mindanao, Philippines Islands.
VMB-443 was commissioned at MCAS Cherry Point on 15 September 1943 and transferred to MCAAF Camp Lejeune on 20 October to continue training. In mid-January 1944, the air echelon and some of the ground echelon went to Naval Auxiliary Air Station (NAAS) Boca Chica, Key West, Florida for torpedo training and tactics and then moved to MCAS El Centro in February in preparation for overseas assignment. The ground echelon sailed from San Diego on 18 May 1944 and arrived at NOB Espiritu Santo in June; one month later, the ground echelon moved to MCAF Emirau and joined the flight echelon which arrived on 13 August. VMB-443 began flying both day and night missions against Rabaul and other bypassed Japanese installations on New Britain and New Ireland Islands until moving to Titcomb Field, Malabang, Mindanao, Philippines Islands in August 1945 after the war had ended.
VMB-611 was commissioned at MCAS Cherry Point on 1 October 1943. After completing training, the squadron transferred to the West Coast and the air echelon sailed from San Diego for MCAS Ewa, Territory of Hawaii on 24 August 1944 with the PBJs tied down on the deck of the escort aircraft carrier USS Manila Bay (CVE-61); the ground echelon sailed for Hawaii on 23 September. While at NAS Barbers Point, Territory of Hawaii, the squadron's PBJs were equipped with underwing zero-length high velocity aircraft rocket (HVAR) launchers and Long Range Navigation (LORAN) equipment. In October, the air echelon flew from Hawaii to MCAF Emirau; both air and ground echelons had arrived by December 1944. VMB-611 flew its first mission on 17 November, a night mission against Kavieg and for the next three months, the squadron flew night heckling missions and strikes against Vanakanau and Tobera on New Britain Island. On 17 March 1945, the ground echelon transferred to Moret Field, Zamboanga (6.54N, 122.05E) on Mindanao Island in the Philippine Islands where it was joined by the air echelon on 30 March. The squadron flew day and night combat missions in the southern Philippines until the end of the war.
VMB-612 was formed at MCAS Cherry Point on 1 October 1943. Beginning in January 1944, the squadron began experiments in low-altitude night-radar operations and alternated operations between NAAS Boca Chica and MCAAF Camp Lejeune for tactical training. In August 1944, the squadron departed the U.S. for Kagman Base on Saipan Island (15.10N, 145.45E) in the Mariana Islands arriving on the island in late October. The air echelon flew to Saipan via MCAS Ewa, Territory of Hawaii where the PBJ-1Ds were modified by the installation of an AN/APN-4 airborne Loran receiver, underwing HVAR rocket launchers synchronized to an AN/APQ-5 airborne radar bombsight, and AN/APN-1 airborne radio altimeters calibrated to give accurate reading between 500 and 1,000 feet (152 and 305 meters). Between 13 November 1944 and February 1945, the squadron flew anti-shipping strikes using rockets against Japanese ships and land targets in the Bonin and Volcano Islands area. After the invasion of Iwo Jima in February, the squadron undertook search missions to the Marcus Island area (24.18N, 153.58E) three nights a week, a mission of 1,450 miles (2,334 km). It was during this period that the squadron began to experiment with the Tiny Tim rocket. The subsonic Tiny Tim had a diameter of 11.75 inches (29.8 cm), a length of 10.25 feet (3.12 m), a firing weight of 1,284 pounds (582.4 kg), and a warhead with an explosive charge weighing 150 pounds (68.04 kg). The Marines modified a Mk 51 bomb rack to carry the rockets and installed two on the belly of the aircraft at the bomb bay. On 1 March, the squadron received three PBJ-1Js and in April 1945, the squadron moved to South Field on Iwo Jima (24.47N, 141.20E) in the Volcano Islands to continue anti-shipping missions. Now within striking range of the Japanese Home Islands, VMB-612 began bombing targets on Kyoto on 10 April. Anti-shipping missions at night, consisting of three PBJs, were unproductive and in the middle of April, daylight raids against the Home Islands commenced. While on Iwo Jima, the squadron had conducted tests and training using the Tiny Tim rocket; the first combat mission with the Tiny Tim, an anti-shipping strike, was flown by a PBJ-1J on the night of 21/22 July from Okinawa but no targets were found. The squadron's final move began on 28 July Chimu Airfield on the eastern shore of Okinawa Island (26.31N, 127.59E) in the Ryukyu Islands. Operations with the Tiny Tims began in earnest on 11 August with one sortie followed by three sorties on 14 August and six sorties during the night of the 14th. With the Japanese surrender, hostilities ceased at 1600 hours Tokyo time on 15 August 1945. The squadron continued experimentation with the Tiny Tims for the rest of the month.
VMB-613 was commissioned on 1 October 1943 at MCAS Cherry Point and transferred to NAS Boca Chica for torpedo training in February 1944, Returning to MCAS Cherry Point in March, VMB-613 moved to MCAF Newport, Arkansas in August for additional training. The air echelon departed MCAF Newport with their PBJ-1Ds for Dyess Field on Roi Island (9.24N, 167.28E), Kwajalein Atoll in the Marshall Islands in October 1944; both air and ground echelons arrived in December and the squadron began operations against bypassed Japanese forces in the Marshalls in January 1945. The forward echelon deployed to Stickell Field on Eniwetok Island (11.30N, 162.15E) in Eniwetok Atoll, Marshall Islands to conduct antisubmarine patrols between 11 January and 13 March 1945. In the spring of 1945, VMB-613 was chosen to test the PBJ-1H and became the only USMC squadron to operate this type of aircraft in combat. The problem was that there were few targets to use the 75 mm gun against and the aircraft was not very effective so on 19 May, four PBJ-1Hs were detached to Iwo Jima to conduct anti-shipping missions but returned to Roi on the 28th without attacking any targets.
VMB-614 was commissioned on 1 October 1943 at MCAS Cherry Point. The squadron trained at Cherry Point plus NAAS Boca Chica and Marine Corps Air Facility (MCAF) Newport. The squadron was initially equipped with PBJ-1C and -1D aircraft and effective in July 1944, with PBJ-1Hs equipped with AN/APG-23 airborne gun directing radar. The PBJ-1H was not a popular aircraft and they were replaced by PBJ-1Js modified with the eight gun nose for low altitude strafing missions. The air echelon departed California on 25 July 1945 followed by the ground echelon in early August; both echelons arrived at Henderson Field, NAS Midway Islands (28.13N, 177.26W) by the end of August 1945.
The eight other squadrons that did not serve in the Pacific were:
VMB-453 was commissioned at MCAS Cherry Point on 25 June 1944; by 31 December 1944, the squadron was equipped with six PBJ-1Ds, three PBJ-1Hs and five PBJ-1Js. VMB-453 decommissioned 20 February 1945 without seeing combat.
VMB-463 was commissioned at MCAS Cherry Point on 20 July 1944; by 31 December 1944, the squadron was equipped with six PBJ-1Hs and two PBJ-1Js. VMB-463 was decommissioned on 28 February 1945 without seeing combat.
VMB-473 was commissioned at MCAS Cherry Point on 25 July 1944 and moved to MCAAF Kinston, North Carolina on 15 December. By the end of December, the squadron was flying one PBJ-1C, one PBJ-1D and two PBJ-1Hs. The squadron was decommissioned on 15 March 1945 without seeing combat.
VMB-483 was commissioned at MCAS Cherry Point on 26 August 1944 and moved to MCAAF Kinston in December; by the end of the month, they were flying two PBJ-1Ds, one PBJ-1G, one PBJ-1H and two PBJ-1Js. The squadron was decommissioned on 15 March 1945 without seeing combat.
VMB-621 was commissioned on 10 April 1944 at MCAS Cherry Point; by the end of December 1944, the squadron had one PBJ-1D, six PBJ-1Hs and one PBJ-1J. The squadron was redesignated Marine Torpedo Bomber Squadron Six Hundred Twenty One (VMTB-621) on 31 January 1945 and re-equipped with Eastern Aircraft TBM Avengers, q.v.
VMB-622 was commissioned on 10 May 1944 at MCAS Cherry Point. The squadron moved to MCAF Newport on 10 September and continued operational training; by the end of December, the squadron was equipped with eight PBJ-1Hs and one PBJ-1J. In February 1945, the squadron moved to MCAS Mojave, California where it was redesignated VMTB-622 on 15 May 1945 and re-equipped with Eastern Aircraft TBM Avengers.
VMB-623 was commissioned on 15 May 1944 at MCAS Cherry Point; by the end of December, the unit had two PBJ-1Ds and 12 PBJ-1Hs. The squadron began operational training with the PBJ but was redesignated VMTB-623 on 10 February 1945 and re-equipped with Eastern Aircraft TBM Avengers.
VMB-624 was commissioned on 20 June 1944 at MCAS Cherry Point. The squadron began operational training with PBJs and by the end of December had ten PBJ-1Hs and one PBJ-1J. On 15 February 1945, the squadron was redesignated VMTB-624 and re-equipped with Eastern Aircraft TBM Avengers.
The seven PBJ squadrons that saw combat in the Pacific suffered the loss of 45 aircraft, 26 in combat and 19 in non-combat operations, and 173 crew, 62 officers and 111 enlisted men.
B-25 SPECIFICATIONS
POWERPLANT: Two 1,700 hp (1,268 kW) Wright R-2600-13 fourteen-cylinder, two-row, air-cooled radial engines with two-speed superchargers driving 12-foot 7-inch (3.84 meter) full-feathering, constant-speed Hamilton Standard three-bladed propellers
WING SPAN: 67 feet 6.7 inches (20.59 meters)
LENGTH
HEIGHT
WING AREA: 609.73 square feet (56.65 square meters)
FUEL CAPACITY (NORMAL): 974 U.S. gallons (3,687 liters)
EMPTY WEIGHT
MAXIMUM WEIGHT
MAXIMUM SPEED
SERVICE CEILING
CREW
RANGE [with 3,000 pound (1,361 kg) bomb load]
ARMAMENT