Mutual defense assistance agreements bound the U.S. Army to the militaries of Latin America by the middle of the 1950s, with only Mexico and Argentina as exceptions. By 1954, the school's pupils were overwhelmingly from Latin American countries due to a decrease in U.S. military personnel in the region, an increased utilization of the school by governments in Latin America, and an agreement that the United States would pay "transportation, per diem and course costs for military trainees from MDAP countries in Latin America." In 1956, English was eliminated as an instructional language and the school adopted Spanish as its official language. Accordingly, the majority of U.S. personnel the school trained between 1956 and 1964 were Puerto Rican.