Green Gang
The Nationalist leader Chiang Kai-shek and the Shanghailanders entered into an informal alliance with the Green Gang, which acted against the Communists and organized labor unions. The nationalists had cooperated with gang leaders since the revolution. Although sporadic fighting between gangsters and communists had occurred previously, many communists were killed in a major surprise attack during the April 12 Incident in the Chinese-administered part of Shanghai. Suspected leftists were shot on sight, so that manyincluding Zhou Enlaifled the city.