While production of the venerable MiGYa-19 continued for decades, the Soviet air forces came to realize that it’s performance would soon no longer be competitive with modern Western variable fighters, and the onset of the First Incursion War spurred the development of a new and more capable design. Using blueprints stolen from the Americans, the Klimov design bureau was able to build the most powerful nuclear thermal turbojet yet made; boasting 20 compressor stages, a new, plutonium-rich fuel mixture, and a massive afterburner, just one of the new engines would be needed to drive the new fighter close to Mach 3. The combined work of the Mikoyan, Gurevich, and Yakovlev design bureaus yielded the MiGYa-21, a fast and agile multirole variable fighter that bridged the performance gap between the capable, but aging heavy interceptors and the nimble but weaker light fighters such as the MiGYa-19. The MiGYa-21, codenamed Falchion, was easily a rival to the newest American variable fighters, and even boasted reentry capability, supercruise, and STOL features all in the same airframe as a result of its variable-geometry wing. Though not the finest dogfighter of the fastest orbital combat craft, the MiGYa-21 represented an extremely capable jack-of-all-trades that scared NATO badly.