Article 9 is a foundational provision of the Constitution of Japan, often called the "Peace Constitution," which came into effect on May 3, 1947. It is a constitutional clause that outlaws war as a means of settling international disputes.
The article's origin lies in the post-World War II occupation of Japan by the Allied Powers, led by General Douglas MacArthur, and was intended to prevent the nation's rearmament and renewed aggression.
The provision works through two key paragraphs. The first paragraph states that the Japanese people "forever renounce war as a sovereign right of the nation and the threat or use of force as means of settling international disputes." The second paragraph is more restrictive, stating that "land, sea, and air forces, as well as other war potential, will never be maintained," and the state's "right of belligerency... will not be recognized."
Despite the second paragraph, Japan maintains the Japan Self-Defense Forces (JSDF), founded in 1954, under an interpretation that they are purely defensive and do not constitute prohibited "war potential." This arrangement is closely connected to the U.S.–Japan Mutual Cooperation and Security Treaty, under which the U.S. provides a security umbrella.
While the article has never been formally amended since 1947, its interpretation has changed recently. In 2014, the cabinet of Prime Minister Shinzo Abe issued a reinterpretation, which was enacted through the Legislation for Peace and Security in 2015. This change allowed the JSDF to exercise the right of collective self-defense—using force to assist an ally—under specific conditions where Japan's survival is threatened.