A startling decree was issued to the population on the third day after Singapore surrendered. All males in Syonan-to between the ages of 18 and 50 years were to report to five registration centres at noon on 12 February 1942.

Meanwhile, the Kempeitai, were dragging people out of their homes at bayonet point. The men were questioned about their names and checked for tattoo marks. The civilians were told to bring along food that could last them for 4 to 5 days. They were not allowed to go home. At night, the centres were guarded by soldiers. Those who were caught attempting to escape were killed. The original idea of the Sook Ching (Purge Through Purification) Operation was to weed out anti-Japanese elements.

The Japanese officials used hooded informants and traitors to identify the Anti-Japanese elements. Those identified were taken away in lorries. It was said that they were taken away for interrogation. But after they were taken away, they were never seen again, not even after the war ended. Those who "failed" the questioning were taken to the beaches of Punggol and Changi to be shot.

Those who passed the screening test were stamped with the word "examined" on their face, arm, clothing or a piece of cloth. The word "examined" was very important to the civilians. It helped them to escape the Japanese soldiers' questioning.

The Sook Ching Operation was an act of reprisal against the Chinese community which had actively supported the war in China against the Japanese and which had participated in the local resistant forces during the Japanese advance into Malaya. Today, the number of Chinese massacred during the Sook Ching Operation is still widely speculated on, but the impact is undeniable. It was an indiscrimate display of criminal butality.