Supreme Commander for the Allied Powers in the context of "British Commonwealth Occupation Force"

Japan was occupied and administered by the Allies of World War II from the surrender of the Empire of Japan on September 2, 1945, at the war's end until the Treaty of San Francisco took effect on April 28, 1952. The occupation, led by the American military with support from the British Commonwealth and under the supervision of the Far Eastern Commission, involved a total of nearly one million Allied soldiers. The occupation was overseen by the US General Douglas MacArthur, who was appointed Supreme Commander for the Allied Powers by the US president Harry S. Truman; MacArthur was succeeded as supreme commander by General Matthew Ridgway in 1951. Unlike in the occupations of Germany and Austria, the Soviet Union had little to no influence in Japan, declining to participate because it did not want to place Soviet troops under MacArthur's direct command.

This foreign presence marks the only time in the history of Japan that it has been occupied by a foreign power. However, unlike in Germany, the Allies never assumed direct control over Japan's civil administration. In the immediate aftermath of Japan's military surrender, the country's government continued to formally operate under the provisions of the Meiji Constitution.

The Constitution of Japan is the supreme law of Japan. Written primarily by American civilian officials during the occupation of Japan after World War II, it was adopted on 3 November 1946 and came into effect on 3 May 1947, succeeding the Meiji Constitution of 1889. The constitution consists of a preamble and 103 articles grouped into 11 chapters. It is based on the principles of popular sovereignty, with the Emperor of Japan as the symbol of the state; pacifism and the renunciation of war; and individual rights.

Upon the surrender of Japan at the end of the war in 1945, Japan was occupied and U.S. General Douglas MacArthur, the Supreme Commander for the Allied Powers, directed Prime Minister Kijūrō Shidehara to draft a new constitution. Shidehara created a committee of Japanese scholars for the task, but MacArthur reversed course in February 1946 and presented a draft created under his own supervision, which was reviewed and modified by the scholars before its adoption. Also known as the "MacArthur Constitution", "Post-war Constitution" (戦後憲法, Sengo-Kenpō), or "Peace Constitution" (平和憲法, Heiwa-Kenpō), it is relatively short at 5,000 signs, less than a quarter the length of the average national constitution if one compares it with constitutions written in alphabetical word-based languages.

Douglas MacArthur (26 January 1880 – 5 April 1964) was an American general who served as a top commander during World War II and the Korean War, achieving the rank of General of the Army. He served with distinction in World War I; as chief of staff of the United States Army from 1930 to 1935; as Supreme Commander, Southwest Pacific Area, from 1942 to 1945 during WWII; as Supreme Commander for the Allied Powers overseeing the occupation of Japan from 1945 to 1951; and as head of the United Nations Command in the Korean War from 1950 to 1951. MacArthur was nominated for the Medal of Honor three times, and awarded it for his WWII service in the Philippines. He is one of only five people to hold the rank of General of the Army, and the only person to hold the rank of Field Marshal in the Philippine Army.

MacArthur, the son of Medal of Honor recipient Arthur MacArthur Jr., was raised on Army posts in the Old West. He was valedictorian of the West Texas Military Academy, and First Captain at the U.S. Military Academy at West Point, where he graduated first in his class in 1903. During the 1914 U.S. occupation of Veracruz, he conducted a reconnaissance mission for which he was nominated for the Medal of Honor. In 1917, he was promoted from major to colonel and became chief of staff of the 42nd (Rainbow) Division. On the Western Front during World War I, he rose to the rank of brigadier general, was again nominated for a Medal of Honor, and was awarded the Distinguished Service Cross twice and the Silver Star seven times. From 1919 to 1922, MacArthur served as Superintendent of the U.S. Military Academy, where he initiated a series of reforms. His next posting was in the Philippines, where in 1924 he was instrumental in quelling the Philippine Scout Mutiny. In 1925, MacArthur became the Army's youngest major general at the age of 45, and in 1930 was appointed Chief of Staff of the U.S. Army. He was involved in the controversial expulsion of the Bonus Army protesters in Washington, D.C., in 1932, and organized the Civilian Conservation Corps. In 1935, MacArthur was appointed Military Advisor to the Commonwealth of the Philippines. He retired from the Army in 1937, but continued as an advisor and as a Field Marshal in the Philippine Army from 1936.

Article 9 of the Constitution of Japan (日本国憲法第9条, Nihon koku kenpō dai kyū-jō) is a clause in the Constitution of Japan outlawing war as a means to settle international disputes involving the state. The Constitution was drafted following the surrender of Japan in World War II. It came into effect on 3 May 1947 during the occupation of Japan by the Allies, which lasted until 28 April 1952. In its text, the state formally renounces the sovereign right of belligerency and aims at an international peace based on justice and order. The article also states that, to accomplish these aims, armed forces with war potential will not be maintained. The Constitution was imposed by U.S. military occupation (Supreme Commander for the Allied Powers) to prevent rearmament of Japan in the post–World War II period. This condition was a similar prohibition placed on post-war Germany, to be overseen by the United Kingdom, after World War I. However, Germany remilitarized anyway in the decades following despite this prohibition under the Weimar Republic and later Adolf Hitler's regime. This was a leading call for the Allied mandate, and the continuing US defense agreements that would render aid in maintaining Japanese sovereignty in the event of a foreign attack.

There are the post-occupation U.S. military stationed in Japan under the U.S.–Japan Mutual Cooperation and Security Treaty and Japan Self-Defense Forces (JSDF) which was founded in 1954 as de facto postwar Japanese military. Prime Minister Shinzo Abe approved a reinterpretation which gave more powers to the JSDF in 2014, which was passed by the Legislation for Peace and Security in 2015.

Kunrei-shiki (Japanese: 訓令式ローマ字, Hepburn: Kunrei-shiki rōmaji; rgh. 'Cabinet-ordered style of Roman letters'), also known as the Monbusho system (named after the endonym for the Ministry of Education, Culture, Sports, Science and Technology) or MEXT system, is a romanization system for transcribing the Japanese language into the Latin alphabet. Its name is rendered Kunreisiki in the system itself. It is taught in the Monbushō-approved elementary school curriculum. The ISO has standardized Kunrei-shiki under ISO 3602.

Kunrei-shiki is based on the older Nihon-shiki romanization, which was modified for modern standard Japanese. For example, the word かなづかい, romanized kanadukai in Nihon-shiki, is pronounced kanazukai in modern standard Japanese and is romanized as such in Kunrei-shiki. The system competes with the older Hepburn romanization system, which was promoted by the SCAP during the Allied occupation of Japan after World War II.

The Japan Self-Defense Forces (Japanese: 自衛隊, Hepburn: Jieitai; JSDF) are the military forces of Japan. The JSDF comprises the Japan Ground Self-Defense Force, the Japan Maritime Self-Defense Force, and the Japan Air Self-Defense Force. They are controlled by the Ministry of Defense with the Prime Minister as commander-in-chief.

The Japanese Constitution, which was adopted by the Supreme Command for the Allied Powers during the occupation of Japan after World War II, stipulates that Japan will never maintain a military as well as other war potential. However, rising tensions during the Cold War led to the reinterpretation of the constitution to allow for the right to self-defense, eventually leading to the creation of the Japan Self-Defense Forces in 1954 that functions as the country's de facto military. Since the end of the Cold War, and particularly into the 21st century, increased tensions with China, North Korea, and Russia have reignited debate over the status of the JSDF and their relationship to Japanese society. The JSDF have maintained a close alliance with the United States, and have prioritized greater cooperation and partnership with Australia, India, Taiwan, South Korea, Singapore, the United Kingdom, and NATO, as well as acquiring new equipment and hardware.

Arahitogami (現人神) is a Japanese word, meaning a kami (or deity) who is a human being. It first appeared in the Nihon Shoki (c. 720) as the words of Yamato Takeru saying: "I am the son of an arahitogami."

In 1946, at the request of the GHQ, the Shōwa Emperor (Hirohito) proclaimed in the Humanity Declaration that he had never been an akitsumikami (現御神), divinity in human form, and claimed his relation to the people did not rely on such a mythological idea but on a historically developed family-like reliance. However, the declaration excluded the word arahitogami.