Imperial Japanese Armed Forces in the context of "Atomic bombings of Hiroshima and Nagasaki"

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 Empire of Japan, also known as the Japanese Empire or Imperial Japan, was the Japanese nation state that existed from the Meiji Restoration on January 3, 1868, until the Constitution of Japan took effect on May 3, 1947. From August 1910 to September 1945, it included the Japanese archipelago, the Kurils, Karafuto, Korea, and Taiwan. The South Seas Mandate and concessions such as the Kwantung Leased Territory were de jure not internal parts of the empire but dependent territories. In the closing stages of World War II, with Japan defeated alongside the rest of the Axis powers, the formalized surrender was issued on September 2, 1945, in compliance with the Potsdam Declaration of the Allies, and the empire's territory subsequently shrunk to cover only the Japanese archipelago resembling modern Japan.

Under the slogans of "Enrich the Country, Strengthen the Armed Forces" and "Promote Industry" which followed the Boshin War and the restoration of power to the emperor from the shogun, Japan underwent a period of large-scale industrialization and militarization, often regarded as the fastest modernization of any country to date. All of these aspects contributed to Japan's emergence as a great power following the First Sino-Japanese War, the Boxer Rebellion, the Russo-Japanese War, and World War I. Economic and political turmoil in the 1920s, including the Great Depression, led to the rise of militarism, nationalism, statism and authoritarianism, during which Japan joined the Axis alliance with Nazi Germany and Fascist Italy, conquering a large part of the Asia–Pacific; during this period, the Imperial Japanese Army (IJA) and the Imperial Japanese Navy (IJN) committed numerous atrocities and war crimes, including the Nanjing Massacre. There has been a debate over defining the political system of Japan as a dictatorship, which has been disputed due by the absence of a dictator, and over calling it fascist. The other suggested terms were para-fascism, militarism, corporatism, totalitarianism, and police state.

Comfort women were women and girls forced into sexual slavery by the Imperial Japanese Armed Forces in occupied countries and territories before and during World War II. The term comfort women is a translation of the Japanese ianfu (慰安婦), a euphemism that literally means "comforting, consoling woman". During World War II, Japanese troops forced hundreds of thousands of women from Australia, Burma, China, the Netherlands, the Philippines, Japan, Korea, Indonesia, East Timor, New Guinea and other countries into sexual enslavement for Japanese soldiers; however, the majority of the women were from Korea. Many women died due to brutal mistreatment and sustained physical and emotional distress. After the war, Japan denied the existence of comfort women, refusing to provide an apology or appropriate restitution. After numerous demands for an apology and the revelation of official records showing the Japanese government's culpability, the Japanese government began to offer an official apology and compensation in the 1990s. However, apologies have been criticized as insincere by victims, advocacy groups, and scholars. Many Japanese government officials have continued to either deny or minimize the existence of comfort women. The Japanese government officially denies that girls and women were coerced into sexual slavery.

Estimates vary on the number of women, with most historians settling somewhere in the range of 20,000–200,000; the exact numbers are still being researched and debated reflecting differences in archival evidence and post war documentation..