The Infantry formation shares the same command as that of the Singapore Army's 9th Division.

On 4 March 1957, young men born and raised in Singapore were recruited to serve in 1 SIR.

Two years later, two more battalions—3 SIR and 4 SIR—were formed when National Service (NS) was introduced in Singapore.

[citation needed] 4 SIR was dissolved on 3 March 2020 after its last mono-intake became operationally ready on 17 January 2020.

[citation needed] On 13 August 2021, the last mono-intake of 6 SIR became operationally ready.