1950s - Singapore/Malaya resisting colonialism. British forces still around & needed (Malayan Emergency), but natives wanna manage internal security. Local defence forces, largely volunteer reserve batteries or squadrons (various combat arms), reorganized under SMF - from SVC - & many served upcountry as frontline as well as freeing up Federal troops for jungle patrolling.
1954-5 - Part-time conscription introduced here. Commie-agitated student riots broke out. NS policy quietly dropped.
1957 - New tack to revived scaling-back of volunteer service: creation of a local regular unit (1 SIR). SMF-SVC-'54 NS vets provided experience. Malaya gained independence, signed AMDA with Britain to mutually protect each other's territories. Singapore's main remained providing naval/airbase facilities, though no more "impregnable fortress."
1959 - Singapore gained self-government. LKY eyed Merger, wary of commies even as Emergency was almost over upcountry. Malaya was receptive, d/n want Singapore as SE Asian "Cuba" ideologically.
1961-2 - Commies agigated over Merger referendum. Barisan Socialis formed. 1 SIR mobilized to help maintain order. 2 SIR formed, but via Malaya-wide recruitment & also staffed by Federal Army troops. Referendum passed.
1963 - Malaysia created. The SIR units joined 7 mainland units to form Federal army of 9 infantry BNs, among other outfits. Malaysia established command structure here (4 MILB) to take control of all local forces from SMF. But AMDA remained primary defence against external threats, as Indonesia declared Confrontation.
1964-5 - Both SIR units sent on 6-month tours to Johor/Sabah to check Indonesian infiltration. 1 SIR would return home barely 4 months before Separation; 2 SIR just 2 months (before redeployed again in August '65 to Sabah for another 6 months).
1965 - Singapore becomes Republic. Military limbo: Counterinsurgency actions continue; ditto British presence despite AMDA invalidated. But internal turmoil too: many Malaysians & Malays transferred to Federal army, for citizenship purposes &/or disinclination to serve a Chinese-majority state. Malaysia also withdrew police riot squad. New MID, under GKS, mobilized for a voluntary PDF for internal security & also recruited regular personnel to offset shortfall.
Early 1966 - SIB created to succeed 4 MIB as command of local forces. Malaysian COs in SIR units also replaced. SAFTI set up. Israeli sent military mission to develop ops & training syllabus. Malaysia refused to leave 2 SIR's base, insisting on right to remain here (as power play). Singapore improvised a logistic contingency, but ended formal bilateral defence cooperation, at least until FPDA in '71.
Later 1966 - Confrontation was fizzling out, leaving Singapore-Malaysia to face off each other without a common enemy, & also Britain publicly hinting about reduction of its SE Asian presence (despite regional persuasion). Escalation of Vietnam conflict & Commie-domino theory amplified regional security fears. Coupled with the need for nation building, Singapore bought wholeheartedly into the citizen-army concept, knowing only conscription could furnish an expanded, credible army.
Early 1967 - All young male civil servants had to attend military training(!). Tabulated National Service bill in Parliament.
Later 1967 - 1st batch of conscripts inducted, trained by newly-graduated instructors & led by SAFTI's pioneering officer batch to form 3 SIR & 4 SIR.
Early 1968 - Britain backtracked on pace of troop withdrawal, opting for a quicker/accelerated pullout. Deadline was brought forward to early '71 (they eventually overshot it), meaning SIngapore had 4 years to take complete control of own defences.
In response, Singapore increased military spending, institutionalized NS at 2 & 2.5 years &, as the units ROD'd, organized them to co-exist alongside active ones & also PDF units at the brigade level. LKY said in his memoirs we had 17 active battalions (16,000 men) & 14 reservist (11,000 men) by 1971. Next phase is the evolution into a professional officer corps, which saw SAF scholarships being awarded to groom future military leaders. LHL was the 1st receipent, slightly ahead of the other Big 4 (TCH, GY, Lim Hng Kiang, Lim Swee Say).