Operation Spectrum
Operation Spectrum, also known as the 1987 "Marxist Conspiracy", was the code name for a covert anti-communist security operation that took place in Singapore on 21 May 1987. Sixteen people were arrested and detained without trial under Singapore's Internal Security Act (ISA) for their alleged involvement in "a Marxist conspiracy to subvert the existing social and political system in Singapore, using communist united front tactics, with a view to establishing a Marxist state." On 20 June 1987, six more people were arrested, bringing the total number of detainees to 22.