For seven months, between October 1945 and April 1946, Castillo Armas received training at Fort Leavenworth, Kansas, where he came in contact with American intelligence officers. After serving on the General Staff, he became director of the military academy until early 1949, at which point he was made the military commander at Mazatenango, Suchitepéquez, a remote military garrison. Castillo Armas had eventually risen to the rank of lieutenant colonel. He was at Mazatenango when Arana launched his failed coup attempt against Arévalo on July 18, 1949, and was killed: Castillo Armas did not hear of the revolt until four days later. Historians differ on what happened to him at this point. Historian Piero Gleijeses writes that Castillo Armas was expelled from the country following the coup attempt against Arévalo. Nick Cullather and Andrew Fraser state that Castillo Armas was arrested in August 1949, that Árbenz had him imprisoned under doubtful charges until December 1949, and that he was found in Honduras a month later.