History of Singapore
During World War 2, Singapore was conquered and occupied by the Japanese Empire from 1942 to 1945. When the war ended, Singapore reverted to British control, with increasing levels of self-government being granted, culminating in Singapore's merger with the Federation of Malaya to form Malaysia in 1963. However, social unrest and disputes between Singapore's ruling People's Action Party and Malaysia's Alliance Party resulted in Singapore's expulsion from Malaysia. Singapore became an independent republic on 9 August 1965.
Japan–Singapore relations
Japan's earliest notable interaction with Singapore occurred while Singapore was still colonized by the United Kingdom as a part of British Malaya. Coinciding with the December 8th surprise attack on the US naval base Pearl Harbor and the same-day attack of the British colony of Hong Kong, the Japanese empire also launched an attack on British Malaya. Japan, having taken control of French Indochina in 1940, was able to launch multiple attacks and, partly due to an alliance with Thailand, took control of large swathes of Malaya over the next two months, concurrently bombing Singapore with increasing frequency. On the 31st of January 1941, Malaya fell to the Japanese, and the last of the retreating Allied forces destroyed the bridge between Malaya and Singapore and began to prepare for a full attack on Singapore.