World War II: The Kempeitai, the military police arm of the Imperial Japanese Army, arrested and tortured fifty-seven civilians and civilian internees on suspicion of their involvement in a raid on Singapore Harbour.

World War II or the Second World War was a global conflict between two coalitions: the Allies and the Axis powers. Nearly all of the world's countries participated, with many nations mobilising all resources in pursuit of total war. Tanks and aircraft played major roles, enabling the strategic bombing of cities and delivery of the first and only nuclear weapons ever used in war. World War II is the deadliest conflict in history, causing the death of 70 to 85 million people, more than half of whom were civilians. Millions died in genocides, including the Holocaust, and by massacres, starvation, and disease. After the Allied victory, Germany, Austria, Japan, and Korea were occupied, and German and Japanese leaders were tried for war crimes.

The Kempeitai , law soldiers, was the military police of the Imperial Japanese Army (IJA). The organization also shared civilian secret police that specialized in clandestine and covert operation, counterinsurgency, counterintelligence, HUMINT, interrogated suspects who might be allied soldiers, spies or members of a resistance movement, maintained security of prisoner of war camps, raided to capture high-value targets, and provided security at important government and military locations at risk of being sabotaged within Japan and its occupied territories. It was notorious for its brutality and role in suppressing dissent. The broad duties of the Kempeitai included maintaining military discipline, enforcing conscription laws, protecting vital military zones, and investigating crimes among soldiers. In occupied areas, it also issued travel permits, recruited labor, arrested resistance, requisitioned food and supplies, spread propaganda, and suppressed anti-Japanese sentiment. At its peak at the end of World War II, the Kempeitai had about 35,000 personnel.

The Imperial Japanese Army was the principal ground force of the Empire of Japan from 1871 to 1945. It played a central role in Japan’s rapid modernization during the Meiji period, fought in numerous conflicts including the First Sino-Japanese War, the Russo-Japanese War, World War I, the Second Sino-Japanese War, and World War II, and became a dominant force in Japanese politics. Initially formed from domain armies after the Meiji Restoration, it evolved into a powerful modern military influenced by French and German models. The IJA was responsible for several overseas military campaigns, including the invasion of Manchuria, involvement in the Boxer Rebellion, and fighting across the Asia-Pacific during the Pacific War. Notorious for committing widespread war crimes, the army was dissolved after Japan's surrender in 1945, and its functions were succeeded by the Japan Ground Self-Defense Force.