High-speed motorized warfare was a new idea at the onset of World War II. The German Army shocked the world with its military successes using the "blitzkrieg" (lightning war). Motorcycle rifle regiments were the fastest of all German army units, and were key elements in the blitzkrieg.
This fact was not lost on American military strategists, but the Harley-Davidson WA and Indian Scout machines used by the US Army were no match in reliability, load capacity, or speed for the BMW and Zundapp equipment used by the Wehrmacht.
In the late summer of 1943, the US War Department issued contracts to develop prototypes of new military motorcycles to both Harley-Davidson and Indian. Harley fulfilled its contract by blatantly copying the BMW R71, producing the XA model. Indian used a more creative approach.
Starting with a 45 cubic-inch Scout engine, Indian spread the cylinder angle out to 90 degrees from 45 degrees, and turned it sideways. A new 4-speed foot-shift gearbox was designed, with an output flange for a driveshaft. The tubular, plunger-suspended frame, and final drive were very similar to the BMW, but the front girder forks were entirely new, and beautifully made out of tapered, oval cross-section tubing.
The resulting machine was remarkably similar to post-war Moto Guzzi V-twins. A total of 1,056 were produced under the prototype contract, but except for a few that were shipped to Army proving grounds, none of them actually saw military service. They were sold as surplus right out of the Indian warehouse in Springfield, for $500 apiece.
This excellent example is owned by Carl Vandre of Denver, Colorado. He reports that the bike is horribly underpowered for its weight, and the gearbox (probably due to lack of development) is weak, very difficult to shift, and prone to early failure. Other than that, it handles well, and the engine is much smoother than any other Indian V-twin, due to the 90 degree cylinder layout. He rides it quite often at gatherings of military vehicle buffs and antique motorcycle events. It never fails to draw a crowd.