In 1933 Pres. Franklin D. Roosevelt (Roosevelt, Franklin D.) appointed Daniels ambassador to Mexico, a post he held until 1944. The appointment was controversial, because in 1914 the U.S. Navy had bombarded the Mexican port of Tampico and had blockaded Veracruz, actions the Mexicans deeply resented. Daniels made special efforts to demonstrate his friendship for the Mexican officials and people; he eventually won their confidence and became Roosevelt's most trusted adviser on issues affecting Mexico. When in 1938–39 Pres. Lázaro Cárdenas expropriated the properties of foreign oil corporations in Mexico, Daniels helped to prevent the incident from disrupting Mexican–U.S. relations.