General William Lendrum ”Billy” Mitchell, US Army (1879-1936) was opinionated, outspoken and argumentative. He foresaw that Japan would be an aggressor in a future conflict, and even that Pearl Harbor would be attacked. In 1921 he demonstrated that the day of the battleship was over by arranging for the sinking from the air of the ex-German Imperial Navy battleship ‘Ostfriesland’ off Chesapeake Bay and successful attacks on other redundant warships. General Mitchell truly was ‘…a prophet who is without honor in his own land.’ He was court-marshalled, but resigned in disgust.
Five years after his death, his predictions came true, and Japanese air power reigned supreme in the Pacific, for a while at least, following the infamous attack on Pearl Harbor. Retribution came in the form of a strike by twin-engined medium bombers, flown from the deck of the USS Hornet, on the Japanese homeland. The aircraft were B-25B Mitchells, built by North American Aviation and named in General Mitchell’s honor, and led by the equally famous Lieutenant Colonel James Doolittle.
Developed by North American Aviation from the unsuccessful XB-21 bomber, the B-25 first flew on 19th August, 1940. Powered by two Wright R-2600 radials, it proved to be a highly adaptable aircraft, and was used for conventional level bombing, low-level attack, torpedo bombing – even photo-reconnaissance. Here you can see a B-25H, powered by Wright R-2600-13 Double Cyclone engines of 1,700 hp, one of the most potent attack aircraft of WW2. It carries a 75mm cannon, as well as up to 14 x .5 inch Browning machineguns in the nose, waist positions, Bendix Model “R” dorsal, and Bell M-7 tail turrets. Originally, the 75mm cannon was an M4 model, but this caused rippling of the aircraft skin, despite strengthening, and in production aircraft the cannon was changed to a T13E1, which was lighter, and caused less structural problems. The B-25H in USAAF service did not carry a co-pilot, the space being occupied by a jump-seat for the navigator/cannoneer/radio operator. The other crew members included pilot, dorsal turret gunner/flight engineer, waist gunner/camera operator and tail gunner. The attack against a target (maritime and riverine targets were more vulnerable than those on land) was usually made in a shallow dive, and fire opened by the pilot, using the N-6A gunsight at around 2,000 yards and broken off at about 1,000 yards, to avoid return fire. The 21 rounds carried were manually loaded by the navigator, and there was time during the average attack run to get three shots on target. The B-25H had arrived in the CBI and SWPA in early 1944, but General George Churchill Kenney, Commanding General of the Far East Air Forces, USAAF, was most displeased at the loss of the co-pilot from the B-25H, as he claimed that pilot fatigue would be far too high on long, over-water, missions that his crews faced.
Strangely, the United States Navy and the Marine Corps who also operated this aircraft – as the PBJ-1H - had a crew of no less than seven! (Pilot, co-pilot, navigator/loader, two waist gunners/radio operators, top turret gunner/engineer, and a tail gunner) Weight was sometimes saved on the Navy/Marine PBJ-1H aircraft by in-the-field modifications which included removal of the dorsal turret (low chance of IJN/JAAF interception at this stage of the war) and deletion of the package guns.
The New England Air Museum’s B-25H seen here (which saw service post-war with the Dominican Air Force - Cuerpo de Aviación Militar Dominicana, at the time) has the florid nose art typical of the B-25 attack groups in the SWPA, and is exhibited with a 75mm cannon alongside.
By the end of 1945, even with a very accurate AN/APG-13 radar ranging set (known as the ‘Falcon’) fitted for use by the navigator/loader, it was found that ‘solid nose’ B-25 Mitchells with multiple .5 inch Brownings could do the job just as well as the 75mm cannon. Given the high parasitic weight of the cannon installation and the structural modifications to strengthen the aircraft, the ‘gun fighter’ hardly seemed worth it. The many other armament options available to the B-25 included 8 x 5 inch HVAR rockets under the wings, for example, which gave a punch larger than the average destroyer broadside. The B-25H was a good idea, but one with a very short shelf life.