On the eve of World War II, the U.S. Army Air Corps ordered hundreds of medium bombers right off the drawing board—before they had even been test flown.
In the late 1930s, U.S. Army Air Corps doctrine had been centered on using multi-engine bombers primarily as long-range strategic weapons. The tactical mission would be carried out by single-engine, two-place aircraft such as the Northrop A-17, as well as by fighters carrying light bombloads. As early as 1936, Air Corps planners had begun to take a keen interest in the activities of the newly emerging German Luftwaffe. In addition to their single-engine dive bombers (referred to generically as Sturzkampfflugzeuge, or “Stukas”), the Germans had developed several types of fast twin-engine attack aircraft that could function in either a tactical or strategic role.
The Air Corps was sufficiently impressed with the Luftwaffe’s order of battle to investigate the possibility of developing similar types of twin-engine aircraft for itself. In March 1938, it issued a circular proposal calling for a light bomber capable of carrying a 1,200- pound bombload over a 600-mile combat radius at speeds in excess of 200 mph. Between late 1938 and early 1939, a fly-off was held to evaluate four prototypes: the Douglas DB-7, Martin 167, North American NA-40 and Stearman X-100.
The Douglas entry was selected for production under the military designation A-20, with an initial order for 100 airplanes, to which 170 more were added before the end of the year. Before the light bomber competition was concluded, however, the Air Corps had begun to formulate a second specification for a larger and heavier twin-engine plane with stepped-up requirements for speed, range and payload.
On March 11, 1939, the Air Corps issued Circular Proposal No. 39-640, calling for a medium bomber with a top speed of 300 mph that would be capable of carrying 3,000 pounds of bombs over a 1,500-mile combat radius. The proposal also directed that the new plane be powered by one of three new air-cooled radial engines under development: the 1,700-hp Wright R-2600, the 1,850-hp Pratt & Whitney R-2800 or the 2,200-hp Wright R-3350 (at the time, only the R-2600 was actually operational).
In a stunning departure from its previous procurement methods, the Air Corps also declared that the winning design would be placed in production, i.e.,“ordered off the drawing board,” before the airplane had flown. Deliveries of production models were expected to commence within 24 months of the contract date, and the deadline for completion of detailed design proposals was set for September 10, 1939.
The North American Aviation Co. of Inglewood, Calif., had already stubbed its toe twice in Air Corps bomber competitions: first in 1937 with the XB-21, which was deemed too expensive compared to the Douglas B-18, and more recently with the NA-40, which lost out to the Douglas A-20. It was a sorry case of bad luck that the sole NA-40 prototype, which had exhibited excellent performance, was accidentally destroyed in the middle of the competition. Although the design was not deemed to be at fault, no government orders had been forthcoming, and the prototype was a complete write-off.
Using the NA-40 as a starting point, the North American design team, led by Lee Atwood as chief engineer, began to work up a new design under the company designation NA-62. This plane would be somewhat larger than its predecessor; wingspan, wing area and fuselage length were increased, and design weight, fully loaded, rose from 20,000 pounds to 28,000 pounds. The narrow fuselage width of the NA-40 was significantly widened to accommodate a larger bomb bay area, resulting in a side-by-side cockpit enclosure that faired into the top of the fuselage line. The high shoulder aspect of the wing was lowered to the mid-fuselage level, and the engine nacelles were faired past the wing’s trailing edge to house the rearward-retracting main landing gear. The general tricycle gear and twin-fin and rudder layout of the NA-40 was retained. For power plants, the team decided on a pair of readily available Wright R-2600-9s, each rated at 1,700 hp for takeoff and 1,500 hp at continuous power settings.
On the opposite side of the continent, in Baltimore, Md., Martin had selected 26-year-old Peyton Magruder to serve as the lead engineer on its medium bomber project. Martin’s new design, designated the Model 179, would be wholly new, bearing virtually no resemblance to the Model 167 (A-22) that the company had previously entered in the light bomber competition. Magruder and his team came up with a low-drag, completely circular fuselage section that gave the plane a decidedly torpedolike appearance from the side. A twin-fin and rudder layout had initially been adopted, but was abandoned in favor of a single-fin arrangement to afford the tail gunner a better field of vision. The airplane would rest on a tricycle landing gear, and the wings would be high shoulder-mounted to the fuselage.
The Model 179’s power would come from a pair of 1,850-hp Pratt & Whitney R-2800-5 engines that, despite never having been used operationally, were the most powerful American-made aircraft engines in existence at the time. Loaded with fuel, ammunition and bombs, the plane would weigh 32,000 pounds. The circular proposal had not specified a maximum landing speed, which was typically 80 to 90 mph for twin-engine planes of the day. Magruder certainly understood that wing area translated to drag, and drag reduced performance, so he calculated a total area that gave the Model 179 wing loading of 51 pounds per square foot—the highest of any American warplane yet flown. Landing speed would be a pavement-scorching 130 mph.
Martin completed its design work first, submitting it to the Air Corps evaluation board at Wright Field on July 5, 1939. The Air Corps was very impressed but reserved any final decisions until the remaining proposals had been submitted and reviewed. The Stearman entry was basically a rehash of its previous X-100/A-21 light bomber design; Douglas reentered its B-23 (a substantial redesign of the B-18, originally intended to compete with the B-17) as a medium bomber candidate; and design proposals received from Consolidated, Vought-Sikorsky and Burnelli were also reviewed. North American’s proposal on the NA-62 was the last to come in, and though it was more conservative than the Martin concept, Air Corps officials felt it represented a major improvement over the earlier NA-40 design.
Using a quality point system to evaluate each design, the Air Corps reported the results on the top three entries in August 1939: Martin’s 179 (designated the B-26) was the winner with 813.6 points; North American’s NA-62 (designated the B-25) came in second with 673.6 points; and Douglas’ B-23 took third with 610.3 points. Surprisingly, when Martin, the hands-down winner, was told that an order would be placed for 385 airplanes, the company informed the Air Corps that it could deliver no more than 201 within the specified 24-month time frame. The Air Corps’ solution to the shortfall was to award the balance of the contract to second-place North American for 184 B-25s.
The decision to buy both planes sight unseen, based on engineering data, was fortunate—more fortunate than the men who bought them could ever have imagined. Whether or not the Air Corps would eventually have ordered a B-25 prototype or placed an order for production test models is a matter of conjecture. In any event, having both planes would be a hedge—in case one of them didn’t work out.
Technically speaking, there was never a prototype for either the B-25 or the B-26, inasmuch as the first plane of each type was considered a production model. The first B-25 reached the final assembly stage in the early summer of 1940 and made its first flight on August 19, with test pilot Vance Breese in the left seat. The first of the next 10 production models were delivered to Wright Field in February 1941. Early flight testing indicated slight directional instability, causing a “Dutch roll” or weave, and the plane also exhibited a reluctance to make flat rudder turns, which were essential to making small course adjustments during a bomb run. Both problems were cured by removing all dihedral from the outer wing panels, a configuration that would give the B-25 its characteristic gull-like appearance from the front. The only other aerodynamic change made was to increase the area of the fins and give them a more squared-off shape. Initial trials with the B-25 revealed excellent performance: a 315-mph top speed at 15,000 feet, a 30,000-foot service ceiling and a 1,400-mile range with a 3,000- pound payload. The bomber also proved to have docile handling qualities, making landing approaches at a leisurely 85 mph.
The first B-25 production models were lightly armed, with three flexibly mounted .30-caliber machine guns in nose, dorsal and waist positions, and one flexibly mounted .50-caliber in the tail, meant to be fired from a prone position. The next 40 planes were produced as the B-25A, introducing steel armor plating for crew protection and self-sealing fuel tanks. The 120 B-25Bs that followed featured upper and lower Bendix L-type power turrets, each containing two .50-caliber machine guns. The upper turret was manned while the lower turret was sighted through a periscope. The periscope sight was ineffective, frequently causing the gunner to suffer from vertigo and nausea, as a result of which the bottom turret was subsequently removed from existing B-models, then deleted altogether on later versions. The next order—right after December 7, 1941—called for 1,625 B-25Cs and 2,290 B-25Ds. A total of 9,815 of all versions would be delivered by the end of 1945.
The maiden flight of the B-26 took place on November 25, 1940, with William K. Ebel at the controls. After 133 hours of flight testing at the factory, the first four production models were delivered to the Air Corps in February 1941. Other than the anticipated high landing speeds, few problems were revealed in the initial testing. The airplane was exceptionally “hot” by the standards of the day, but its general flying characteristics, including single-engine operations, were good, though certainly not docile. Early testing showed a top speed of 315 mph, a service ceiling of 25,000 feet and a 1,000-mile range with bombload. Though slightly smaller than the B-25, the B-26 was heavier by 3,500 pounds, with most of the additional weight incorporated into its structure, a feature that would prove very beneficial later on.
The B-26 was the first American aircraft designed from the start with the installation of a power-operated turret. The Martin-designed dorsal turret, located just ahead of the tail fin, was equipped with two .50-caliber machine guns. Other armament included flexible .30- caliber mounts in the nose and in the belly aft of the bomb bay and a .50-caliber mount in the tail operated by the gunner in an upright position. The original contract was followed by an order for 109 B-26As (19 of which were delivered to the RAF), featuring improvements to the electrical system, additional armor plating and increased fuel capacity. The next order was for 1,883 B-26Bs—in all, 5,157 would be produced before production terminated in March 1945.
Because America’s Lend-Lease clients assigned names rather than designators to various aircraft types, the factories began to give their aircraft official names. Martin wanted something that started with the letter “M” and proposed the name Martian for the B-26, but the RAF quickly dubbed it the Marauder, which became official later on. Legend has it that Lee Atwood selected the name Mitchell for the B-25 to honor the late air power prophet Brig. Gen. William “Billy” Mitchell, making it the only Allied plane of the wartime era actually named for an individual.
Production B-25s first went into operational service with the 17th Bombardment Group, based at McChord Field in Washington state, in the spring of 1941. This unit would more than any other bring the Mitchell to combat-ready status. Volunteers from the 17th made up the crews of the 16 B-25Bs that launched from the flight deck of the aircaft carrier Hornet on April 18, 1942, in the famous first attack on the Japanese Home Islands led by Lt. Col. James H. Doolittle.
Throughout 1942 new B-25 units were formed and introduced to combat in the Mediterranean and Pacific theaters of operations. The South Pacific–based Fifth Air Force determined early on that seaborne and dispersed land-based targets were extremely difficult to hit from medium altitudes (10,000-14,000 feet). The solution they pioneered was to switch the B-25s to low altitude skip-bombing, releasing the bombs from 200-250 feet very close to the target and allowing them to “skip” across the surface of the water to the point of impact. Since this technique required a very low approach straight into concentrated anti-aircraft fire, much heavier forward-firing armament was needed to suppress enemy defenses.
Major Paul I. “Pappy” Gunn of the 3rd Bombardment Group based in Australia came up with the idea of turning the B-25C into a “strafer.” The bombardier’s station was removed from the nose and replaced with four fixed .50-caliber machine guns with four more fixed .50- caliber guns added to the sides of the fuselage in blister packs. The strafer modification was so successful in combat operations that follow-on B-25G and B-25H models were built with factory-installed guns instead of glazed noses. It was a credit to the versatility of the B-25’s general design that it could be so extensively modified yet still possess above-average handling qualities.
The B-25 became the U.S. Army Air Forces’ standard medium bomber for the China-Burma-India (Tenth and Fourteenth Air forces), Southwest Pacific (Fifth and Thirteenth Air forces) and Pacific theaters (Seventh Air Force), and was used along with the B-26 in the North African/Mediterranean campaign (Twelfth Air Force). The B-26 had been used early in the Pacific campaign, but was not as adaptable to the low-level strafer role, nor, with its higher takeoff and landing speeds, was it as capable of operating from the many forward bases with shorter runways. B-25s were also employed during the Pacific campaign in small numbers by the U.S. Navy and Marine Corps under the designation PBJ.
The introduction of B-26 Marauders into service was not nearly as smooth as that of its B-25 stablemate. The 22nd Bombardment Group, based at Langley Field, Va., took delivery of its first B-26s in February 1941, replacing its B-18s. The unit was plagued with a series of nose landing gear strut failures, attributed initially to high landing speeds but ultimately traced to improper loading, which had moved the center of gravity so far forward that it exceeded the design loads on the nose gear. The 22nd was deployed to Australia in the spring of 1942 and flew its first combat sortie on April 5, attacking Japanese military installations at Rabaul, New Britain. In the following months the B-26s of the 22nd flew from Australia to bomb Japanese targets in Java, New Britain and New Guinea.
In the first days of June 1942, four B-26As that were each configured to carry a single 2,000-pound torpedo were sent to Midway Atoll in anticipation of a Japanese attack. On June 4, the four planes took off to intercept the Japanese carrier force en route to Midway. The Marauders were required to start their runs at 800 feet, then drop down to wave-top level to launch their torpedos. Flying into the teeth of the concentrated antiaircraft fire and Mitsubishi A6M2 Zero fighters, two of the B-26s were shot down, and no hits were made on any of the ships. This ended any future plans to use Marauders as torpedo bombers.
Disaster struck in mid-1942 while B-26 operational training units were forming at MacDill Field in Tampa, Fla. In addition to the fact that nearly all of the new pilots were fresh out of flight training and possessed zero multi-engine experience, a problem with the electrical system emerged on early B-26 models that shorted out the control circuits on the Curtiss propellers, causing a dangerous phenomenon known as a “runaway prop.” This condition was prone to occur most often during the takeoff run, while the engines were running at full power. The accident rate in B-26 training became so scandalous—34 crashes involving 56 pilot/instructor fatalities in 1942—that aircrews came to consider the plane a deathtrap, labeling it the “Martin Murderer,” the “Widow Maker” and the “Flying Prostitute” (i.e., no visible means of support) and similar epithets.
Following a recommendation by the U.S. Senate to cancel Martin’s production contract, an investigation team headed by Jimmy Doolittle (then a brigadier general) was sent to MacDill in October 1942. Doolittle reported that the chief cause of most of the accidents had been inadequate training, and single-engine recovery techniques in particular. He recommended new methods and urged that new pilots receive some multiengine training prior to converting to the B-26. After the training program was modified, B-26 accident rates quickly dropped to a range comparable to other training units operating similar types of aircraft.
New B-26 combat units joined the Eleventh Air Force in the Aleutians, the Twelfth Air Force in North Africa and the Eighth Air Force in England. The 319th Bombardment Group became the first unit to enter combat, flying a medium altitude sortie over Tunisia in December 1942.
In May 1943, Marauders of the Eighth Air Force 322nd Bombardment Group were sent on two low-level raids against a power plant at Ijmuiden on the Dutch coast. The German defenses were surprised by the first attack, but the time delay on the fuzes allowed the Germans to disarm all of the bombs before they exploded. When a flight of 11 B-26s attacked the same target again three days later, all but one aircraft (which had aborted before reaching the target) were destroyed by flak and fighters. Following this debacle, all European theater–based B-26s were placed on indefinite stand-down, and consideration was again given to removing the type from combat.
Marauders attached to the Eighth Air Force resumed combat operations in July 1943, bombing from medium altitudes and accompanied by fighter escort this time. In October all Marauder units in England were transferred to the Ninth Air Force, where the groups engaged in medium-altitude precision bombing of targets like bridges, airfields, railroad marshalling yards and supply dumps. As it turned out, the B-26 was the ideal medium bombing platform for the flak-infested higher-altitude war of the European theater. Early combat experience had brought about the addition of four fixed .50-caliber “package guns” mounted on the fuselage sides plus one additional fixed .50-caliber mounted in the glazed nose, bringing total forward-firing armament to 10 .50-caliber guns. Luftwaffe fighters became reluctant to make close-in attacks in the face of the massed firepower of group strength (i.e., 96 aircraft) Marauder formations.
After D-Day, Ninth Air Force B-26s followed the invading Allied armies to the Continent, continuing to fly medium-altitude missions against tactical targets until V-E Day on May 3, 1945. Despite their disastrous start, B-26s in the European theater flew more missions and destroyed more targets with fewer losses than any other type of bomber flying in that combat theater.
In the huge downsizing that followed the end of World War II, U.S. Army Air Forces (U.S. Air Force after 1947) planners decided to keep only the newer Douglas A-26 Invader to operate in the medium bomber/attack role. The B-25, however, was retained as the Air Force’s standard multi-engine trainer, and many also served in utility roles and with Air National Guard units up through the 1950s.
Some B-25s are still flying today, while many others are preserved in museums. The B-26 did not fare as well: Those serving with Ninth Air Force units were left behind in Europe to be cut up for scrap, while planes consigned to storage in Stateside facilities suffered a similar fate during the immediate postwar years. By 1949, virtually all of them had disappeared; today only one B-26 is still flying, and a few others are on static display in air museums.
E.R. Johnson is a frequent contributor to Aviation History. Additional reading: Marauder Men: An Account of the Martin B-26, by John O. Moench; and The B-25 Mitchell at War, by Jerry Scotts.
Originally published in the May 2007 issue of Aviation History. To subscribe, click here.