Cause
The death of Chinese Premier Zhou Enlai on January 8, 1976, prompted the protest. Zhou Enlai was a widely respected senior Chinese leader. For several years before his death, he was involved in a political power struggle with other senior leaders in the Politburo of the Communist Party of China.
Premier Zhou's most visible and powerful antagonists were the four senior members who came to be called the Gang of Four. The leader of the clique, Jiang Qing, was married to Communist Party Chairman Mao Zedong. To defuse an expected popular outpouring of sentiment at Zhou's death, the Communist Party of China limited the period of public mourning; for example, the national flag was lowered to half-mast for only one hour.
Read more about this topic: Tiananmen Incident