After World War II, the relationship between the U.S. and Japan evolved from being adversaries to allies. The U.S. occupied Japan from 1945 to 1952 and played a significant role in the country's post-war reconstruction, including the implementation of democratic reforms and the modernization of the economy.
The U.S. and Japan signed the Treaty of Mutual Cooperation and Security in 1960, which established a security alliance between the two countries and provided for U.S. military bases in Japan.
Since then, the U.S. and Japan have developed a close economic and diplomatic relationship, with Japan becoming one of the United States' closest allies and largest trading partners. The two countries have worked together on various global issues, including promoting free trade and supporting international security.
Therefore, the statement that BEST describes the relationship of the U.S. and Japan after World War II is:
The U.S. and Japan went from being adversaries to becoming allies, with a close economic and diplomatic relationship, including a security alliance and collaboration on global issues.