In the early part of 1939, the United States Army Air Corps (USAAC) drew up plans for a new generation of medium bomber types that were rather recently embodied by the Douglas B-18 "Bolo" and B-23 "Dragon" forms (the Dragon essentially becoming an evolution of the Bolo). The Specification of March 1939 called for a twin-engined form flying at speeds of 300 miles-per-hour out to a range of 2,000 miles all the while carrying a bomb load of up to 3,000lb.
The requirement was eventually fulfilled by two of the more classic design forms of World War 2 - the North American B-25 "Mitchell" (the NA-62) and the Martin B-26 "Marauder" (the Model 179). Both excelled in their given roles and the designs were considerably evolved from their original offerings to help fulfill wartime requirements.
However, before the Model 179 would become the excellent B-26, it underwent a period of constant change. As early as July 1939, the aircraft was a twin-engined design of portly appearance with a deep, rounded fuselage. The fuselage's nosecap was completely glazed over and the cockpit (also heavily framed) was stepped (consistent with the final-form, in-service B-26 still to come). The aircraft was given a twin-rudder fin tail unit set slightly ahead of the tapered, terminating end of the fuselage. The wing mainplanes sat shoulder-mounted atop the fuselage and each carried an underslung engine nacelle, the engines used to drive four-bladed propeller units with oversized spinners. The undercarriage was a rather modern tricycle formation in which the main legs retracted into the engine nacelles and the nose leg into the underside of the forward fuselage. A crew of five would make up the operators required for the various onboard systems including pilots, flight engineer, bombardier, and gunners.
As proposed, the Model 179 had an overall length of 57.4 feet with a wingspan of 65 feet and a height of 14.8 feet. MTOW was rated at just over 29,000lb.
Power would come from 2 x Pratt & Whitney (PW) R-2800-5 air-cooled radial piston engines of 1,850 horsepower output or 2 x Wright R-2600 radials of 1,700 horsepower. This arrangement was to supply the medium bomber with a maximum speed of up to 325 miles-per-hour out to a range of 3,000 miles and operating at altitudes up to 26,500 feet - all exceeding the USAAC original requirements. The warload reached 2,000lb and this could be pushed as high as 2,400lb.
The Martin design was submitted for consideration on July 5th, 1939 and accepted against other supplied competitors. This resulted in a production order for 201 aircraft under the "B-26" in-service designation and, even before the actual aircraft had flown, the USAAC pushed through another production order for 930 additional bombers. By this time, the twin-tail configuration was dropped in favor of a single vertical tail fin with a pair of horizontal planes and the overall design of the aircraft was considerably streamlined for the better. In about twenty-four months, this "paper airplane" was finalized and flew into war time service - and American military aviation history - as the "Marauder" (detailed elsewhere on this site).