During World War II, Singapore was occupied by the Empire of Japan, marking a pivotal moment in the histories of Japan, Britain, and Singapore. Post the British surrender on 15 February 1942, the city was renamed "Syonan-to," translating to "Light of the South Island." The Japanese military police, the Kempeitai, took control and introduced the "Sook Ching" system, which aimed to eliminate those they perceived as threats, particularly ethnic Chinese. This led to the Sook Ching massacre, where an estimated 25,000 to 55,000 ethnic Chinese were executed. The Kempeitai also established a vast network of informants to single out anti-Japanese elements and imposed a strict regime where civilians had to show overt respect to Japanese soldiers and officials.

Life under Japanese rule was marked by significant changes and hardships. To counter Western influence, the Japanese introduced their educational system, compelling locals to learn the Japanese language and culture. Resources became scarce, leading to hyperinflation and making basic necessities like food and medicine hard to come by. The Japanese introduced "Banana Money" as the primary currency, but its value plummeted due to rampant printing, leading to a thriving black market. With rice becoming a luxury, locals relied on sweet potatoes, tapiocas, and yams as staples, leading to innovative dishes to break the monotony. Residents were encouraged to grow their own food, akin to "Victory Gardens" in Europe.

After enduring years of occupation, Singapore was formally returned to British colonial rule on 12 September 1945. The British resumed administration, but the occupation had left a lasting impact on the Singaporean psyche. Confidence in British governance was deeply shaken, with many believing that the British were no longer capable of effectively administering and defending the colony. This sentiment sowed the seeds for a rising nationalist fervor and the eventual push for independence.