The Thirtieth of September Movement (Indonesian: Gerakan 30 September, abbreviated as G30S, also known with the acronym Gestapu for Gerakan September Tiga Puluh or sometimes called Gestok, for Gerakan Satu Oktober, First of October Movement) was a self-proclaimed organization of Indonesian National Armed Forces members who, in the early hours of 1 October 1965, assassinated six Indonesian Army generals in an abortive coup d'état. Later that morning, the organization declared that it was in control of media and communication outlets and had taken President Sukarno under its protection. By the end of the day, the coup attempt had failed in Jakarta at least. Meanwhile, in central Java there was an attempt to take control over an army division and several cities. By the time this rebellion was put down, two more senior officers were dead.
In the days and weeks that followed, the army blamed the coup attempt on the Indonesian Communist Party (PKI). Soon a campaign of mass killing was underway, which resulted in the death of hundreds of thousands of alleged communists.
September 30 is the 273rd day of the year (274th in leap years) in the Gregorian calendar. There are 92 days remaining until the end of the year.