William George Stirling was Assistant Protector of Chinese in Singapore from 1921 to 1931, and he studied Chinese secret societies extensively both during and after his tenure. The William Stirling Collection includes numerous objects and documents that had been seized from the secret societies during police raids after the societies were declared illegal by the British colonial government in 1890. Secret societies in Singapore originated from the Tiandihui (Heaven and Earth Society) in China, a sworn fraternity of men with the common aim of overthrowing the Qing dynasty and restoring the Ming. With the influx of Chinese workers to Singapore in the 19th century, the society became a form of mutual-aid and support, but gradually evolved to become large crime syndicates. They were forced underground after 1890 and had become little more than street gangs by the middle of the 20th century.