The US–Japan Mutual Security Treaty was a pivotal agreement established to fortify cooperation between the United States and Japan in the context of the Cold War. Signed in Washington, D.C., by U.S. Secretary of State Christian Herter and Japanese Foreign Minister Zorin, the treaty came after years of negotiation and reflects the shifting global landscape of the time. Japan had undergone significant changes following World War II, including a new constitution that renounced war and established a pacifist stance. However, the rise of communism in Asia, alongside tensions from the Korean War, pushed Japan to seek a partnership with the United States for security and stability.

The treaty outlined that both nations would consider an armed attack against Japan as an attack against both, thereby creating a collective defense mechanism. It also allowed the U.S. military to maintain bases in Japan, which was crucial for America's military strategy in the Asia-Pacific region. The treaty marked Japan's re-entry into the international security community post-war, fostering an environment for economic growth and democratic governance.

Despite its significance, the treaty faced domestic opposition in Japan, leading to widespread protests that highlighted the complexities of Japan's national identity and its relationship with the United States. These protests indicated a strong desire among some Japanese citizens for greater autonomy and a critique of foreign military presence in their country, intensifying the debate over Japan's sovereignty and military policy.