On 12 April 1927, Chiang Kai-shek's KMT launched a coup against his Communist allies and massacred them in Shanghai. The surviving Communists went underground and established its intelligence agency, the Special Service Section (known by its Chinese abbreviation Teke), led by Zhou Enlai. Because of Li's experience in bomb-making and his familiarity with Shanghai's Green Gang, Zhou and Gu Shunzhang recruited him into Teke and made him head of communications, one of Teke's four divisions. Li developed a close friendship with Gu, head of the Red Squad or Teke's assassination team, and Chen Geng, head of intelligence. They worked together in the failed mission to rescue the captured Communist leader Peng Pai, but successfully assassinated Bai Xin, the turncoat who had betrayed Peng.