By: Warren Gray

Copyright © 2021

“In every battle, there comes a time when both sides consider themselves beaten, then he who continues the attack wins.”

— General Ulysses S. Grant.

The North American Aviation (NAA) B-25 Mitchell medium bomber holds the rare distinction of being the first American, military aircraft named for a person, Brigadier General William Lendrum “Billy” Mitchell of the U.S. Army Air Service, a daring, flamboyant, outspoken, combat-veteran and aviation pioneer, who is widely regarded as the father of the U.S. Air Force. He commanded all American air combat units in France during the First World War, actually flying some missions himself, and earning the Distinguished Service Cross and the Distinguished Service Medal, among many others.

After the war, Mitchell became a tireless and relentless advocate for air power and an independent air force, severely antagonizing the U.S. Navy at the time, especially after a series of bombing demonstrations in 1921, in which his bombers easily sank an ex-German destroyer, a light cruiser, and finally, the mighty, ex-German battleship Ostfriesland, within a mere 22 minutes. These bombing tests immediately changed the entire outlook of the U.S. Armed Forces, with air power gaining a newfound respect that clearly revealed naval weaknesses.

After visiting Hawaii on an inspection tour in 1924, Mitchell wrote a scathing, 324-page report, predicting a Japanese, surprise, aerial attack on Pearl Harbor 17 years before it actually came to pass. But his brash and impulsive nature got him into deep trouble with military leadership in 1925, especially after he issued a statement accusing senior officers of an “almost treasonable administration of the national defense” for ignoring the obvious benefits of air power, and he was court-martialed for insubordination by 13 judges, none of whom had any aviation experience, was found guilty, and resigned from the service on February 1, 1926. He died 10 years later.

However, very soon after the terrible, Japanese attack on Pearl Harbor in 1941 proved Mitchell to be absolutely correct, vindicating him completely, he was posthumously promoted to major general, and had the brand-new, B-25 Mitchell bomber named in his memory. During World War Two, many warships were sunk solely by air attacks, again proving Mitchell to be a visionary leader. In 1946, his family was awarded a special, one-of-a-kind, Congressional Gold Medal, “in recognition of his outstanding, pioneer service and foresight in the field of American military aviation.” He was later inducted into the National Aviation Hall of Fame and the International Air and Space Hall of Fame.

The B-25 Mitchell bomber itself was introduced into the U.S. Army Air Corps in late 1941, and was produced in far greater numbers (9,816 built) than any American, twin-engine bomber. It entered service in 1942, and had its combat debut on the famous, “Doolittle Raid” of April 18, 1942, in which Lieutenant Colonel James H. “Jimmy” Doolittle valiantly led a formation of 16 modified, stripped-down, B-25BMitchells from the aircraft carrier USS Hornet at wavetop level to the Japanese homeland, a mere four months after the devastating, Japanese attack against Pearl Harbor, striking military targets in downtown Tokyo, Yokohama, Yokosuka, Nagoya, and Kobe, to demoralize the Japanese public. The raid caused very little permanent damage to enemy industry, but it was a tremendous morale boost and psychological victory for U.S. forces.

The B-25 was rugged, sturdy, well-armored, exceptionally-stable, easy to fly for new pilots, and relatively fast (340 mph top speed) for a bomber, produced in Inglewood, California (3,208 aircraft, with “-NA” suffix), and Kansas City, Kansas (6,608 aircraft, only the B-25D and J variants, with “-NC” suffix.) Although it began service as a medium bomber, with a plexiglas nose and bombardier station, NAA also began working on a specialized, gunship variant for low-level, ground-attack missions, and was soon alternating production batches between pure bombers and special “strafers,” or attackers, with a solid, metal-covered nose bristling with machine guns, and initially, a massive, 75mm cannon!

Many variants were manufactured in rapid order, capable of carrying up to 3,600 pounds of bombs, plus a variety of gun armaments, and combat experience led to the introduction of crew armor, self-sealing fuel tanks, upgraded engines, and by late 1942, an initial, gunship concept. The B-25G-model had a short, solid nose containing two fixed, Browning M2 heavy machine guns in .50-caliber, and an M4 75mm cannon, by far the largest gun ever fitted to any aircraft, although the German Henschel Hs 129B-3 ground-attack aircraft also mounted a BK 7.5 75mm cannon, for anti-tank use.

The massive, 905-pound, M4 gun, however, was manually loaded, fired only single shots, was clumsy to operate, its heavy weight reduced aircraft performance, the navigator had to double as a cannon-loader, and it had horrendous, bone-jarring recoil, often damaging the B-25G’s airframe in combat use, despite being mounted in a moving cradle (the weapon kicked back 21 inches during firing) to reduce the recoil forces.

This concept then evolved into the B-25H version, with the same short nose, but with four M2 machine guns in the nose instead of two, four blister-mounted, forward-firing, M2 guns on the sides of the fuselage, a lighter-weight, T13E1 (M5) 75mm cannon (still with tremendous recoil), two more M2 guns in a tail turret, and a pair of waist guns behind the bomb-bay area. The top turret was moved forward, just behind the cockpit area, with two additional guns, for a better field of view. This gave the B-25H a total of 14 machine guns, eight of them fixed and forward-firing, and the huge cannon.

In actual combat, though, its performance was disappointing, slow and cumbersome to employ, with a very low rate of fire, tremendous recoil, and a firing trajectory much different from the .50-caliber, M2 nose guns. The B-25H could be fitted with kits for eight 127mm (five-inch) High-Velocity, Aircraft Rockets (HVARs), nicknamed “Holy Moses,” which proved far more accurate, powerful, and effective in the heat of battle. The massive cannon was relatively unpopular with aircrews, and was often removed in war zones to improve aircraft performance.

The B-25H-1, however, was chosen by Lieutenant Colonel Philip G. “Phil” Cochran in 1944 to equip the 1st Air Commando Group, the forerunners of today’s Air Force special operations units, because they could be flown almost as aggressively as fighters, and he hired mostly fighter pilots to man his aircraft.

There was a semi-humorous anecdote about a B-25H pilot over the Aegean Sea near Greece, searching for German resupply boats to target. He had very little faith in his 75mm cannon, but would sometimes discharge a round just for fun. One day, he actually hit a German vessel, and he and his copilot stared at each other for several seconds in utter amazement. Then he dryly commented, “Don’t tell anyone we did this. They might think it was a good idea.”

Dissatisfaction with the B-25Gand B-25H gunships led to the introduction of the B-25J-model, which was originally intended to revert back to the bomber role, with a plexiglas nose and bombardier inside, and in fact, about half of them were equipped as ordinary, medium bombers. This was the final variantof the venerable Mitchell, introduced in December 1943 and produced in the greatest numbers (4,318 completed.) It was basically a B-25H from the cockpit aft, including the four M2 “blister” guns on the sides, with the glass nose and four fixed, nose guns of the B-25D-model, plus a bombardier’s fifth nose gun. A number of sub-variants were manufactured, including the J-5, J-10, J-11, J-15, J-20, J-22, and J-32 designations, all with the “-NC” suffix of the Kansas City plant.

However, North American Aviation also produced an alternate, “strafer” nose section, called the B-25J-2 nose, initially shipped to air depots as kits, and then later fully incorporated onto new aircraft. This nose housed eight M2 heavy machine guns in two vertical columns of four guns each, and there was no 75mm cannon anymore. In addition, the top gun turret, just behind the cockpit, could be rotated forward, adding two more weapons for low level strafing. This was a combined total of 14 forward-firing, Browning M2 heavy machine guns, with an overall, throw weight of approximately 215 pounds of projectiles per second, and one very late version carried 18 forward-firing guns!

This absolutely devastating array of firepower was largely thanks to the ingenious, combined efforts of Major General (later Lieutenant General) George C. Kenney, commander of the Fifth Air Force in the Southwest Pacific, and Captain (later Colonel) Paul Irving “Pappy” Gunn, who first met each other at Charters Tower Airfield near Townsville, Australia, on August 5, 1942, where the grizzled, 42-year-old Gunn was expertly supervising the do-it-yourself, clearly-unauthorized installation of quad .50-caliber machine guns into the nose of an A-20A Havoc twin-engine, attack aircraft, using fully-functional weapons salvaged from wrecked, American fighter planes.

Pappy Gunn was quite an interesting character, an eccentric, cigar-chomping, freewheeling maverick. He enlisted in the U.S. Navy as an aircraft mechanic near the end of the First World War, later learned to fly airplanes, purchased his own private aircraft, and became a Navy fighter pilot and instructor pilot, eventually retiring from the service in 1939 to start a charter, flying service in Hawaii, and then an airline in the Philippines.

When World War Two began, Pappy was commissioned as a captain in the U.S. Army Air Corps, flying reconnaissance and support missions due to his age, but he still managed to earn a Distinguished Flying Cross (DFC) for flying medical supplies to the besieged, American troops on the Bataan Peninsula. Gunn was widely known as “an expert in daredevil, low-level flying,” recognized for numerous feats of heroism (also earning a second DFC, the Silver Star, Legion of Merit, Air Medal, and nine Purple Hearts for being repeatedly wounded in combat), as well as for his mechanical ingenuity.

Kenney, quite a talented pilot himself, with two air-to-air victories during the First World War, was described by his boss, General Douglas MacArthur, as “born 300 years too late, a natural-born pirate,” and was a true gun-lover. He was instantly impressed by Gunn’s innovative abilities, made him his personal, “Special Projects Officer,” and had him modify 16 more A-20As within the next two weeks, including the addition of bomb racks to hold 40 small, 23-pound, M40 “para-frag” (parachute-retarded, fragmentation) bombs.

These same aircraft were used on a highly-successful mission against the Japanese airfield at Buna, New Guinea, on September 12, 1942, so Kenney gave Gunn carte blanche to convert an entire squadron of B-25 Mitchells into low-level strafers, each with a dozen forward-firing guns, and they played a major role in the February-March 1943 Battle of the Bismarck Sea, sinking four cargo vessels and two destroyers in just the first 15 minutes of their combat action, and earning Gunn a well-deserved promotion to major. Kenney and Gunn called their aircraft “commerce-destroyers,” since they usually attacked Japanese shipping and resupply boats.

Next, Pappy was sent back to the United States to oversee North American Aviation’s incorporation of his armament innovations into the B-25G, H, and J-models, developing and perfecting the “strafer” nose configuration. He later returned to Australia with Jack Fox, an NAA technical representative, who assisted him with modifying B-25Cs and Ds into “Gunn-ships” (based upon Gunn’s last name) with four nose guns and two or four blister guns on the sides. Pappy was seriously wounded in the arm during a Japanese attack on Leyte, the Philippines, in late 1944, and he ultimately retired from the Army in 1948 as a full colonel, and died in a charter-plane crash in a storm in the Philippines in 1957.

Japanese propaganda broadcasts criticized Kenney’s and Gunn’s “new and fiendish methods of warfare,” calling the American aviators “gangsters.” The B-25 pilots from Fifth Air Force were now employing daring, new, anti-shipping tactics, including two methods developed with the help of the Royal Air Force and the Royal Australian Air Force, skip-bombing and mast-height bombing. The B-25’s speed (272 mph with a full bomb load) made it particularly effective at these attack techniques, plus low-level strafing with its fearsome, nose armament.

Skip-bombing was exceptionally hazardous, because the B-25 had to fly very low over the water, peppering the enemy vessel with its nose guns to suppress defensive fire, and then release a bomb with a time-delay fuze to skip over the water and slam into the Japanese ship’s hull, hopefully exploding after the low-flying Mitchell was clear of the target vessel on the far side. There was great danger from the enemy antiaircraft guns, avoiding the ship’s masts, and the possibility of the bomb skipping back up into the air and striking the B-25 instead.

But it was also a murderously-effective technique, combat-proven with resounding success in the Battle of the Bismarck Sea. In fact, because the B-25 lacked a defensive, gun turret in the belly and was therefore vulnerable to attack from below, the pilots actually preferred to fly as low and as fast as possible, to avoid enemy fighters. The crews of these early, modified B-25Cs and Ds from the 3rd Attack Group flew so perilously low that they jokingly claimed that if they came across a local farmer’s cow in a field on one of their missions, they’d simply fly around it!

B-25 Mitchell medium bombers were used in Europe, North Africa, Alaska, and the Middle East by the 12th, 28th, 310th, 319th, 321st, and 340th Bombardment Groups, and in the Pacific Theater of Operations (PTO) by the 3rd, 22nd, 38th, 41st, 42nd, 341st, and 345th Bombardment Groups. By far, the majority of Mitchells saw action in the Pacific region.

They also served with the Royal Air Force, Royal Australian Air Force, Royal Canadian Air Force, Free French Air Force, Nationalist Chinese Air Force, Brazilian Air Force, Dutch Air Force in exile, and Soviet Air Force. Even General Dwight D. Eisenhower, the Supreme Allied Commander in Europe himself, used a bare-metal, highly-modified, VB-25J-1-NCas his personal transport, with all guns removed. It’s currently on display at Ellsworth Air Force Base, South Dakota.

The B-25J was powered by two Wright R-2600-29 Twin Cyclone 14-cylinder, dual-row, air-cooled, radial, piston engines, each producing 1,700 horsepower, with 1,850 emergency horsepower available. The “strafer” version had a five-man crew: pilot, navigator (sitting in the unoccupied, copilot seat), top-turret gunner, radio operator/waist gunner, and tail gunner. The only competing, American gunship aircraft of the war were the A-20 Havoc, introduced in 1941, and the A-26 Invader, introduced in September 1943, but the B-25 gunship was simpler and substantially less-expensive to construct, had longer range, and by the end of the war, the B-25J-series was the most-heavily-armed aircraft in the U.S. Army Air Forces inventory.

The B-25J-2 “strafer” armament usua
lly consisted of eight Browning M2 heavy machine guns in the nose, and four more M2s in the blister mounts, each with 400 rounds per gun, two M2 guns in the top turret with 400 rounds per gun, two M2 waist guns with 250 rounds per gun, and twin tail guns with 600 rounds per gun. M8 armor-piercing incendiary (API) ammunition was frequently used due to its devastating effects. Later in the war, many of the side-mounted, blister guns were removed in the field, in order to reduce weight and aerodynamic drag, since the eight forward-firing, nose guns were deemed sufficient for strafing missions. Strangely, the pilot had only simple, iron sights for aiming this vast array of powerful machine guns.

The bomb bay could hold up to 3,000 pounds of munitions, including 23-pound, M40 para-frag bombs, 100-pound M30A1bombs, 250-pound M57 bombs, 500-pound M64A1bombs, 1,000-pound, M65A1 bombs, 1,600-pound armor-piercing bombs, or 325-pound depth charges. HVAR rockets could be mounted beneath the wings using special kits.

One of the most-colorful of the B-25C/D/J gunship combat units was the 345th Bombardment Group (“Air Apaches”), with an Indian-head insignia on their tail surfaces, serving primarily in New Guinea, the Dutch East Indies, and the Philippines. The group had four squadrons, the most-active of which were the 498th Bombardment Squadron (“Falcons”) and the 499th Bombardment Squadron (“Bats Outta Hell.”)

In fact, the wartime photograph at the beginning of this article depicts a B-25J-22 gunship from the 499th Bombardment Squadron, flown by First Lieutenant Francis A. Thompson, attacking and sinking a heavily-armed, Japanese Type C (No. 1) escort vessel in the Taiwan Strait near Amoy (Xiamen), China, on April 6, 1945. Note the bold, aggressive, black, bat’s face and white teeth painted on the nose of the aircraft, with bat’s wings extending backward along both sides, to the rear edges of the cockpit area. The side-mounted, blister guns were deleted by then, and the top, gun turret was swiveled forward for additional firepower.

The B-25J-22-model was the first to incorporate the J-2 “strafer” nose from the NAA factory in Kansas City, not as a later modification. One very positive benefit of having all machine guns clustered together in the nose, and of the same model and caliber, was that the weapons always aimed true in the horizontal plane, all had exactly the same ballistic trajectory, and there was no convergence zone to worry about, which was the case with wing-mounted guns. So, the pilot could open fire at any range out to about 2,000 yards, and the gunfire would be concentrated and deadly-accurate.

The 499th Bombardment Squadron arrived in Australia in April 1943, only a month after Pappy Gunn’s successful gunship attacks in the Bismarck Sea, and their B-25s were stationed at Port Moresby, New Guinea, by June 1943. In-theater, these initial batches of B-25Cs and Ds were modified with additional nose guns for strafing attacks, and they flew their first combat mission on June 30, 1943, operating from New Guinea for the next year, where they became especially adept at strafing Japanese airfields or ships, as well as flying vital, armed-reconnaissance missions.

In November 1943, the “Bats Outta Hell” attacked a series of antiaircraft gun batteries, barracks, and coastal defenses near the Japanese naval base at Rabaul, New Britain, earning a Distinguished Unit Citation (DUC), and in December 1943, they began receiving improved, B-25Js. By mid-1944, they had earned a second DUC, and advanced to the Dutch East Indies, attacking enemy airfields and shipping in the Philippines, where they finally landed in November 1944.

From there, the “Bats” struck Japanese targets as far away as Formosa (Taiwan), earning a third DUC for an attack on Saigon, French Indochina. One photo accompanying this article shows a B-25J-10 Mitchell, nicknamed “Jaunty Jo,” with a bombardier nose section, of the 345th Bombardment Group flying over the Byoritsu oil refinery on the island of Formosa on May 26, 1945, and releasing a series of tiny, para-frag bombs. The B-25 has been hit by Japanese antiaircraft fire from a camouflaged battery, and is trailing smoke, with a gaping hole in the pilot’s side of the aircraft.

By July 1945, shortly before the Japanese surrender, the 499th had moved forward to Ie Shima Airfield in the Ryuku Islands, attacking shipping in the Sea of Japan. Meanwhile, other B-25 gunship units became experts at destroying enemy-held bridges in Burma. One squadron jokingly nicknamed itself the “Dental Clinic” because it was so adept at bridgework.

In conclusion, the devastating, B-25J-2 Mitchell gunship rapidly became the most-heavily-armed, most-formidable, most-successful, low-level attack aircraft of World War Two, arriving on target completely by surprise by flying beneath radar-detection altitude, relentlessly pounding enemy ground gunners, ships, or parked aircraft with their machine guns first, then bombing them or firing rockets on the way out, and again disappearing below radar coverage as they exited the battle zone. This was, in fact, the striking, wartime origin of the modern, American term, “gunship.”

Warren Gray is a retired, U.S. Air Force intelligence officer with experience in joint special operations and counterterrorism. He served in Europe and the Middle East, earned Air Force and Navy parachutist wings, and four college degrees, including a Master of Aeronautical Science degree, and was a distinguished graduate of the Air Force Intelligence Operations Specialist Course, and the USAF Combat Targeting School. He is currently a published author and historian. You may visit his web site at: