Despite not holding the presidency, Calles remained the key political figure during the period known as the Maximato (1929–1934). The Maximato ended during the presidency of Lázaro Cárdenas, who expelled Calles from the country and implemented many economic and social reforms. This included the Mexican oil expropriation in March 1938, which nationalized the U.S. and Anglo-Dutch oil company known as the Mexican Eagle Petroleum Company. This movement would result in the creation of the state-owned Mexican oil company Pemex. This sparked a diplomatic crisis with the countries whose citizens had lost businesses by Cárdenas's radical measure, but since then the company has played an important role in the economic development of Mexico. Cárdenas's successor, Manuel Ávila Camacho (1940–1946) was more moderate, and relations between the U.S. and Mexico vastly improved during World War II, when Mexico was a significant ally, providing manpower and materiel to aid the war effort.