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.
History of the Republic of Singapore
After gaining independence abruptly, Singapore sensed the need for immediate international recognition of its sovereignty. The Konfrontasi was ongoing and some UMNO factions strongly opposed the separation; Singapore faced the danger of being attacked by Indonesian military or forcibly reabsorbed into Malaysia on disadvantageous terms. With the support of the Malaysian, Republic of China, and Indian governments, Singapore became a member of the United Nations on 21 September 1965, and the Commonwealth in October that year.