The Japanese occupied Singapore from 1942 until 1945. They designated it the capital of Japan's southern region and renamed it Shonan, meaning "Light of the South" in Japanese. All European and Australian prisoners were interned at Changi on the eastern end of the island--the 2,300 civilians at the prison and the more than 15,000 military personnel at nearby Selarang barracks. The 600 Malay and 45,000 Indian troops were assembled by the Japanese and urged to transfer their allegiance to the emperor of Japan. Many refused and were executed, tortured, imprisoned, or sent as forced laborers to Thailand, Sumatra, or New Guinea. Under pressure, about 20,000 Indian troops joined the Japanese-sponsored Indian National Army to fight for India's independence from the British.

The Asian civilian population watched with shock as their colonial rulers and supposed protectors were marched off to prison and the Japanese set about establishing their administration and authority. The Chinese were to bear the brunt of the occupation, in retribution for support given by Singapore Chinese to China in its struggle against Japan. All Chinese males from ages eighteen to fifty were required to report to registration camps for screening. The Japanese or military police arrested those alleged to be antiJapanese , meaning those who were singled out by informers or who were teachers, journalists, intellectuals, or even former servants of the British. Some were imprisoned, but most were executed, and estimates of their number range from 5,000 to 25,000. Many of the leaders of Singapore's anti-Japanese movement had already escaped, however, and the remnants of Dalforce and other Chinese irregular units had fled to the peninsula, where they formed the Malayan People's Anti-Japanese Army.

The harsh treatment by the Japanese in the early days of the occupation undermined any later efforts to enlist the support of Singaporeans for the Japanese vision of a Greater East Asia CoProsperity Sphere, which was to comprise Japan, China, Manchuria, and Southeast Asia. Singapore's prominent Chinese leaders and businessmen were further disaffected when the Japanese military command bullied them into raising a S$10 million "gift" to the Japanese as a symbol of their cooperation and as reparation for their support for the government of China in its war against Japan. The Chinese and English schools were pressured to use Japanese as the medium of instruction. The Malay schools were allowed to use Malay, which was considered the indigenous language. The Japanesecontrolled schools concentrated on physical training and teaching Japanese patriotic songs and propaganda. Most parents kept their children at home, and total enrollment for all the schools was never more than 7,000. Although free Japanese language classes were given at night and bonuses and promotions awarded to those who learned the language, efforts to replace English and Chinese with Japanese were generally unsuccessful.

Serious disruption of not only the economy but the whole fabric of society marked the occupation years in Singapore. Food and essential materials were in short supply since the entrepôt trade that Singapore depended on to provide most goods was severely curtailed by the war. Chinese businessmen collaborated with corrupt Japanese officials to establish a flourishing black market for most items, which were sold at outrageous prices. Inflation grew even more rampant as Japanese military scrip flooded the economy. Speculation, profiteering, bribery, and corruption were the order of the day, and lawlessness against the occupation government almost a point of honor.

As the war wound down and Japanese fortunes began to fade, life grew even more difficult in Shonan. Military prisoners, who suffered increasing hardship from reduced rations and brutal treatment, were set to work constructing an airfield at Changi, which was completed in May 1945. Not only prisoners of war but also Singapore's unemployed civilians were impressed into work gangs for labor on the Burma-Siam railroad, from which many never returned. As conditions worsened and news of Japanese defeats filtered in, Singaporeans anxiously awaited what they feared would be a bloody and protracted fight to reoccupy the island. Although Japan formally surrendered to the Allies on August 15, 1945, it was not announced in the Singapore press until a week later. The Japanese military quietly retreated to an internment camp they had prepared at Jurong. On September 5, Commonwealth troops arrived aboard British warships, cheered by wildly enthusiastic Singaporeans, who lined the five-kilometer parade route. A week later, on the steps of the municipal building, the Japanese military command in Singapore surrendered to the supreme Allied commander in Southeast Asia, Admiral Lord Louis Mountbatten.

Data as of December 1989