Sook Ching was a mass killing that occurred from 18 February to 4 March 1942 in Singapore after it fell to the Japanese. It was a systematic purge and massacre of 'anti-Japanese' elements in Singapore, with the Singaporean Chinese particularly targeted by the Japanese military during the occupation. However, Japanese soldiers engaged in indiscriminate killing, and did not try to identify who was 'anti-Japanese.' Singapore was a crucial strategic point in World War II. From 8 February to 15 February, the Japanese had fought for control of the city. The combined British and Commonwealth forces surrendered in a stunning defeat to the outnumbered Japanese on 15 February which led to its fall. The loss of Singapore was and still is Britain's largest surrender in history. Three days later after the fall on 18 February, the occupying Japanese military began mass killings of a wide range of "undesirables", who were mostly ethnic Chinese, influenced by the events of the Second Sino-Japanese War that was raging simultaneously as far back as 1937. The operation was overseen by the Imperial Japanese Army's Kempeitai, its secret police. Along with Singapore, Sook Ching was subsequently also extended to include the Chinese population in Malaya, which was also under occupation by the Japanese. Concurrently, non-Chinese individuals were also not completely spared in other parts of Asia under Japanese occupation; the Japanese had also killed at least 150,000 Tamil Indians as well as an additional 90,000 civilians in Burma and Thailand, many of which were also forced to work on the Siam–Burma Railway, infamously known as the Death Railway. The aim for such a purge was to intimidate the Chinese community, which was considered by the Japanese to be potentially the main centre of resistance to Japanese aims of territorial expansion throughout the Asia-Pacific. The Japanese had also thought of it as a "revenge" for their perceived anti-Japanese activity in the Sinophone regions, such as procuring financial aid for China after the Japanese invasion of Manchuria and during the Second Sino-Japanese War. As a consequence, Sook Ching was aimed primarily at Chinese political and social activists, volunteers fighting on the side of the Allies, as well as representatives of Chinese triads. In practice, however, the arrests and executions were carried out by the Japanese in a completely arbitrary manner, with many civilians randomly killed in summary executions even if they took no part in any organised resistance.