Since the nineteenth century, peninsula Malaya and Singapore have formed essentially one economic and military unit under British colonial rule. As Malaysia and Singapore moved towards independence, political leaders on both sides of the causeway accepted as an article of faith that their mutual defence was indivisible. The continuing presence of British military forces, based mainly in Singapore, reinforced this view. The political leadership of Singapore's People's Action Party (PAP), who agitated for an end to colonial rule, concluded that an independent Singapore would not be militarily viable on its own and that Singapore's defence and security needs could best be met through merger.

Up until separation from Malaysia in August 1965, Singapore's military forces have always been an adjunct of outside powers, first of Britain and then Malaysia. Indeed, at independence in September 1963, the Singapore Armed Forces (SAF) were incorporated in and came under the operational control of the Malaysian Armed Forces. These arrangements resulted in the recruitment of a military force that was overwhelmingly peninsular Malay in ethnic composition. The presence of Malaysian troops on Singapore's territory and the ethnic composition of Singapore's armed forces at the time of separation proved catalysts in the development of an ethnically Chinese SAF and a defence doctrine that stressed deterrence against threats by Malaysia.

The origins of Singaporean military forces can be traced back to 1854 with the formation of the Singapore Volunteer Rifle Corps. In 1934, the Straits Settlements Royal Naval Volunteer Reserve was created, comprising mainly small coastal patrol boats. In the mid-1950s the land forces were filled out by the addition of national servicemen and part-time conscripts. Singapore's first professional military force was created in 1957 when the Singapore Infantry Regiment (SIR) was formed. Singapore maintained a small air element until 1960 when it was disbanded.

Peninsula Malaya gained its independence on 31 August 1957. Under the terms of the Anglo-Malayan Defence Agreement (AMDA), which came into force in October, Great Britain and Malaya agreed to “take all necessary action” in the event of an armed attack on Malaya or British territories in the Far East. Britain was permitted to retain its military bases and forces in Malaya. Britain also agreed to assist in the development of the Malayan armed forces and to fund the SIR's second battalion.