Overview History of the B-25 Mitchell
The B-25 had originated in 1938 when the AAF had issued a circular proposal for a twin engine medium attack bomber, Spec. #98-102. North American, of Inglewood, California, produced a twin engine, twin tailed bomber with tricycle landing gear, high wing and clean aerodynamic configuration. The pilot and co-pilot sat side by side with the bombardier-navigator in a glass nose protected by a .30 caliber machine gun. There was a dorsal turret manned by a radio-gunner, and two other .30 caliber guns mounted on the midline of the fuselage. The maximum bomb load was 1,200lbs., it carried 476 gallons of fuel and was powered by 1,100HP Pratt and Whitney engines. Gross weight was 19,500lbs. In January, 1939 the first NA prototype (NA-40-1) was flown, and then a second prototype with improvements was tested shortly afterward (NA-40-2). The original was found to be underpowered, so the engines were changed to Wright Cyclones (1350HP) which increased the aircraft's speed. The NA-40-2 was destroyed in a crash in the spring of 1939, but the AAF liked the potential they had seen and asked for some further modifications to the original design. The third prototype, NA-62, was improved aerodynamically with a smoother nose cone than before and a tail cone with .50 caliber guns for rear protection. On September 10, 1939, the AAF approved and gave the plane the designation XB-25. The war in Europe sped production of the original contract of 184 planes. The most famous version of the B-25 would be the B-25B, used by Jimmy Doolittle in April, 1942. Doolittle led an attack against Tokyo with B-25B's launched from a Navy aircraft carrier. As the war progressed, North American responded to suggestions from the flyers themselves, and improvements and updates were constantly being made, and by December, 1943 production of the B-25D stopped in North American's Kansas City plant to begin production on the B-25J, which was the last and most numerous model produced, 4,318 being produced during the last two years of the war. It carried a crew of six, a ton and one half of bombs, and had a top speed of 332MPH.
In the Pacific during 1942, many B-25's began their conversion to strafers. The bottom turret was removed and fared over and an extra gas tank put in its place. The greenhouse nose was rebuilt and four .50 caliber guns mounted on a small metal nose cap. Two machine gun side packs were put on each side of the plane, just below the cockpit, giving the B-25's eight forward firing .50's. The gun switch was wired to the cockpit on a button on the pilot's control wheel. The .50 caliber machine guns would give crews a tremendous advantage as they literally chewed up everything in their path, and crew members quickly learned to get their planes down and use them at close range. Crew chiefs often shook their head in disbelief as planes came home with green propellers from the jungle foliage, coconuts wedged into nacelles, and even pieces of Japanese ships blown into the planes. The Mitchell strafers used their guns and parafrags on strikes at Japanese jungle bases, but developed a basic attack plan on Japanese shipping which developed from experience. In order to use the firepower of the Mitchell most effectively, they would approach low, usually on the stern of the ship. They liked to come in stern to bow, which they felt gave them a larger area for bombing and restricted the enemy's anti-aircraft fire. It was also easier to stay with a ship evasive turns in this fashion. As the Mitchell approached in a shallow dive, it opened up with the .50's in the nose and sidepacks. This much fire often disabled much of the ship's defenses and also caused a great deal of confusion, which enabled the pilot to bomb accurately. The B-25 would fly over the ship's mast, then head "down on the deck" and take evasive action in making their escape. The element of surprise was essential; crews were instructed to make only one pass over enemy shipping. If an enemy was waiting and ready for you, a B-25 at that height would be difficult to miss.
Some groups experimented with the B-25H, which incorporated a .75mm gun in the nose along with four .50's. Instead of a co-pilot, they had a cannoneer to load the gun. Though potentially a deadly weapon, the gun caused the plane to be nose heavy, slower and the blast usually filled the cockpit with smoke. The crews claimed the plane seemed to stop in mid-air when the gun was fired. The B-25H was replaced in August, 1944 by the B-25J. The J model could have the clear bombardier nose or be converted with a kit supplied by North American, into a strafer with eight .50's in the nose, giving the plane a total of eighteen .50 caliber machine guns, fourteen firing forward. This easily made the J model the lethal medium bomber of the war, a virtual gunship.
If you are interested in reading about a Bomb Group in the Pacific that used the Mitchell with great effectiveness, look at the section on the 345th BG and/or read the article I have written on my uncle's experiences with the Air Apaches.