Phú Yên province on 2 January 1833. The ruler of Vietnam at the time, Emperor Minh Mạng, was not eager to allow foreigners to freely enter Vietnam and engage in trade. The emperor required that Americans follow Vietnamese laws, and only allowed them to do business in Da Nang, Central Vietnam. After receiving this unwelcome message, Edmund Roberts and his delegation left Vietnam. The American-Vietnamese relationship remained frozen after many disagreements and tensions from 1836 to 1859. This lasted until 1873, when Vietnam had trouble fighting against the invading French forces in northern Vietnam. Emperor Tự Đức appointed Foreign Minister Bùi Viện as "Grand Emissary" and sent him to the United States to seek support and aid against the French Empire. The diplomatic delegation passed through Yokohama, Japan, then arrived in San Francisco in mid-1873. Bùi Viện and the Vietnamese emissaries traveled to Washington, D.C. and met with U.S. President Ulysses S. Grant, who promised aid and an alliance with Vietnam. However, the U.S. Congress cancelled Grant's intervention in Vietnam. In 1884, Vietnam was completely conquered by France, becoming French Indochina. World War II The U.S. and Vietnam had informal relations during World War II, though this was not directly with French Indochina. Though the U.S. had good relations with the French Third Republic, after the latter fell to Nazi Germany in 1940, Germany established Vichy France, which took over administration of the French colonies, including French Indochina. Vichy France allowed the Empire of Japan to access French Indochina, and in July 1941 Japan extended its control to the whole of French Indochina. During the Pacific War, American agents of the Office of Strategic Services, led by United States Army officer Archimedes Patti, arrived in Vietnam and met with the Viet Minh, a communist independence movement led by pro-American revolutionary Ho Chi Minh. The OSS and the Viet Minh cooperated together to fight Japanese forces in French Indochina, and the OSS trained the Viet Minh, who gave the OSS agents shelter. The People's Army of Vietnam, founded in 1944 in the mountains of northwest Vietnam, had been backed and supported by the OSS and trained by American military personnel, including Patti, who greatly respected the Vietnamese. The first commander of the PAVN was Võ Nguyên Giáp, who was trained under the watch of the Americans. The relations between the Viet Minh and the OSS marked the beginning of American involvement