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Internal Security Department

Our history

Learn about Internal Security Department's history.

Last updated 24 September 2025
ISD’s vigilance and interventions have kept Singapore safe and secure, and allowed our nation to develop and grow.
— Former Prime Minister Lee Hsien Loong (2008)

ISD’s history is inextricably intertwined with Singapore’s security history. We trace our roots to the Criminal Intelligence Department (CID) of the colonial police service, which was set up in 1918 in the wake of what was named the Sepoy Mutiny of 1915. The CID was renamed Special Branch in 1933 to reflect its responsibility in dealing with a range of pre-war threats posed by communists, seditionists and spies.

Black and white profile pictures of Rene Onraet, Prithvi Chand, Balwant Singh and Wong Chin Yoke.

Early pioneer officers such as (from left to right) Director of CID Rene Onraet, Chief Inspector Prithvi Chand, Chief Inspector Balwant Singh and Senior Asiatic Inspector Wong Chin Yoke were involved in the fight against seditionists, spies and subversives during the pre-war period.

During Singapore’s tumultuous road to independence after World War II, the Singapore Special Branch dealt with internal security threats arising from communal (racial and/or religious) tensions, communist subversion and foreign operatives looking to wreak havoc here during the period known as Konfrontasi.

Black and white photo of a vehicle on fire in the middle of a road.

Vehicles were set on fire and damaged during the Maria Hertogh Riots.

Large crowd gathered outside a building during the Maria Hertogh riots.

On 17 February 1966, after Separation from Malaysia, the Singapore Special Branch was renamed the Internal Security Department (ISD). ISD had to grapple with serious security challenges confronting a fledgling nation. With the Cold War in full swing, the Communist Party of Malaya continued to pose a serious threat to national security with its campaign of violence. Foreign countries, even friendly ones, attempted to influence our domestic politics. Terrorism also reared its ugly head as Singapore became a target for hostile actors and extremist militant groups.

ISD has safeguarded Singapore’s internal security, stability and sovereignty for decades. We continue to do so, as the longstanding security threats of terrorism, communal extremism, foreign subversion and interference, and espionage, persist and evolve while new threats emerge in an increasingly complex world.

Pivotal events:

The Sepoy Mutiny of 1915

The 1915 sepoy mutiny in Singapore, driven by anti-colonial sentiment and seditious influence, led to civilian deaths and spurred the formation of the Criminal Intelligence Department in 1918.

The Communist Threat

From 1948 to the late 1980s, Singapore faced violent communist insurgency and subversion led by the Communist Party of Malaya, which was eventually defeated through sustained security operations by the Special Branch and ISD.