One of the most controversial American combat aircraft of the Second World War was the Martin B-26 Marauder. It was primarily used in Europe and was in fact numerically the most important USAAF medium bomber used in that theatre of action. However, on four occasions, investigation boards had met to decide if the development and production of the Marauder should continue.

In spite of this, the Marauder survived all attempts to remove it from service. By 1944, the B-26s of the US 9th Air Force had the lowest loss rate on operational missions of any American aircraft in the European theatre, reaching a point less than one half of one percent. Despite its high landing speed of 130 mph, which remained essentially unchanged throughout the entire production career of the B-26 in spite of numerous modifications made to reduce it, the Marauder had no really vicious flying characteristics and its single-engine performance was actually fairly good. Although at one time the B-26 was considered so dangerous an aircraft that aircrews tried to avoid getting assigned to Marauder-equipped units and civilian ferry crews actually refused to fly B-26s, it turned out that the Marauder could be safely flown if crews were adequately trained and knew what they were doing. It nevertheless did demand somewhat of a higher standard of training for its crews than did its stablemate, the B-25 Mitchell. Once mastered however, the B-26 offered a level of operational immunity to its crews unmatched by any other aircraft in its class.

A total of 5157 B-26 Marauders were built. Although on paper the B-26 was a more advanced aircraft than the North American B-25 Mitchell, it was built in much fewer numbers because it was more expensive to manufacture and had a higher accident rate (even though the accidents were mainly due to insufficient training and not inherently bad design).

The Martin Marauder's history dates back to early 1939. Both the North American B-25 Mitchell and the Martin B-26 Marauder owe their origin to the same Army Air Corps specification. On March 11, 1939, the Air Corps issued a proposal for the design of a new medium bomber. According to the requirements listed in the specification, a bombload of 3000 pounds was to be carried over a range of 2000 miles at a top speed of over 300 mph and at a service ceiling exceeding 20,000 feet. The crew was to be five and armament was to consist of four 0.30-inch machine guns. The proposal called for either the Pratt & Whitney R-2800, the Wright R-2600, or the Wright R-3350 radial engine.

Four aircraft manufacturers responded with proposals, Martin, Douglas, Stearman and North American. Since the Army wanted a high maximum speed but hadn't specified any limitation on landing speed, the Martin team selected a high-mounted wing with a wingspan of only 65 feet. Its small area gave a wing loading of more than 50 pounds per square foot. The wing was shoulder-mounted to leave the central fuselage free for bomb stowage. The fuselage had a low-drag profile with a circular cross section.

The engines were to be a pair of 1850 hp Pratt & Whitney R-2800-5 Double Wasp air-cooled radials, which were the most powerful engines available at the time. Two-speed mechanical superchargers were installed in order to maintain engine power up to medium altitudes and ejector exhausts vented on each side of the closely-cowled nacelles. The engines drove four-bladed 13 foot 6 inch Curtiss Electric propellers. Large spinners were fitted to the propellers and root cuffs were added to aid in engine cooling. In all, the armament included two 30 calibre machine guns and three 50 calibre machine guns including one in the tail and another installed in the tip of a transparent nose cone and operated by the bombardier. The tail gunner had enough room to sit in an upright position, unlike the prone position that had been provided in the early B-25.

There were two bomb bays, fore and aft. The bomb bay doors were unusual in being split in tandem, the forward pair folding in half when opened and the aft set being hinged normally to open outward. Two 2000-lb bombs could be carried in the main bomb bay, but up to 4800 pounds of smaller bombs could be carried if the aft bay was used as well.

The Martin design was rated the highest of those submitted and on August 10, 1939, the Army issued a contract for 201 Model 179s under the designation B-26. Although the first B-26 had yet to fly, orders for 139 B-26As with self-sealing tanks and armor were issued on September 16. Further orders for 719 B-26Bs on September 28, 1940 brought the total B-26 order to 1131 aircraft.

A series of failures of the front wheel strut resulted in a delay in bringing the B-26 to full operational status. Although the forward landing gear strut was strengthened in an attempt to correct this problem, the true cause was an improper weight distribution. The manufacturer had been forced to deliver the first few B-26s without guns and had trimmed them for delivery flights by carefully loading service tools and spare parts as ballast. When the Army took the planes over, they removed the ballast without replacement and the resultant forward movement of the center of gravity had multiplied the loads on the nosewheel, causing the accidents. The installations of the guns called for in the original design corrected the problem.

The last B-26 was delivered in October of 1941. That month, the Martin Middle River production line shifted over to the B-26A version, which really was the same aircraft with a few modifications.