Japan–United States relations

International relations between Japan and the United States began in the late 18th and early 19th century with the diplomatic but force-backed missions of U.S. ship captains James Glynn and Matthew C. Perry to the Tokugawa shogunate. Following the Meiji Restoration, the countries maintained relatively cordial relations. Potential disputes were resolved. Japan acknowledged American control of Hawaii and the Philippines, and the United States reciprocated regarding Korea. Disagreements about Japanese immigration to the U.S. were resolved in 1907. The two were allies against Germany in World War I.

From as early as 1879 and continuing through most of the first four decades of the 1900s influential Japanese statesmen such as Prince Iesato Tokugawa (1863–1940) and Baron Eiichi Shibusawa (1840–1931) led a major Japanese domestic and international movement advocating goodwill and mutual respect with the United States. Their friendship with the U.S. included allying with seven U.S. presidents – Grant, Theodore Roosevelt, Taft, Wilson, Harding, Hoover, and Franklin D. Roosevelt. It was only after the passing of this older generation of diplomats and humanitarians, along with the evidence that many Americans believed all Asians to be alike with President Calvin Coolidge's signing of the Immigration Act of 1924 that Japanese militarists were able to gain control and pressure Japan into joining with the Axis Powers in World War II.

Starting in 1931, tensions escalated. Japanese actions against China in 1931 and especially after 1937 during the Second Sino-Japanese War caused the United States to cut off the oil and steel Japan required for their military conquests. Japan responded with attacks on the Allies, including the surprise attack on Pearl Harbor on December 7, 1941, which heavily damaged the US naval base at Pearl Harbor, opening the Pacific theater of World War II. The United States made a massive investment in naval power and systematically destroyed Japan's offensive capabilities while island hopping across the Pacific. To force a surrender, the Americans systematically bombed Japanese cities, culminating in the atomic bombings of Hiroshima and Nagasaki in August 1945. Japan surrendered, and was subjected to seven years of military occupation by the United States, during which the Americans under General Douglas MacArthur eliminated militarism and rebuilt the country's economic and political systems.

In the 1950s and 1960s Japan entered into a military alliance with the United States, and experienced unprecedented economic growth by sheltering under the U.S. nuclear umbrella, taking full advantage of U.S.-backed free trade schemes, and supplying American wars in Korea and Vietnam. Japanese exports to the United States dramatically expanded in the postwar period, with Japanese automobiles and consumer electronics being especially popular, and Japan became the world's second largest economy after the United States (in 2010 it dropped to third place after China). From the late 20th century and onwards, the United States and Japan have had firm and active political, economic and military relationships. US government officials generally consider Japan to be one of its closest allies and partners. Most Americans generally perceive Japan positively, with 84% viewing Japan favorably in 2021; however, few Americans consider Japan one of their closest allies in public opinion polls, with only 1% of Americans picking Japan as their most important foreign policy partners, far behind other key American allies, according to a 2021 Pew survey. In a New York Times analysis of YouGov data in 2017, American survey respondents ranked Japan as their 21st closest ally, also behind other key American allies. Japan is currently one of the most pro-American countries in the world, with 67% of Japanese viewing the United States favorably, according to a 2018 Pew survey; and 75% saying they trust the United States as opposed to 7% for China. In a 2019 Pew survey, 63% of people in Japan named the United States their closest ally, far higher than any other country named by Japanese respondents.