[1] With the creation of the new Communist government, Wang Dongxing was named deputy director of the General Office of the Chinese Communist Party (an important bureaucratic position dealing with administration and personnel) and, crucially, Director of the 9th Bureau of the Ministry of Public Security, in charge of Mao Zedong's personal security detail, and also of protecting Zhongnanhai, the seat of government power.
Mao trusted Wang, and made him responsible for checking the background of all staff serving in Zhongnanhai (not only bodyguards, but also waiters, cooks, secretaries etc.)
For "his efforts in public security work", Wang was awarded the rank of Major General of the Chinese People's Liberation Army, also in 1955.
On orders from Hua Guofeng (Mao's designated successor) he assembled a group of trusted officers, made them swear an oath of loyalty and secrecy, and instructed them to "shoot to kill" if there was any armed resistance.
[1] In the event, no blood was shed: Jiang Qing's three close associates (Zhang Chunqiao, Yao Wenyuan and Wang Hongwen) were quickly and easily arrested after being lured to a high-level meeting in Zhongnanhai, ostensibly to discuss the building of Mao's Mausoleum and the publication of his latest works.
Wang Dongxing and his patron Hua Guofeng were gradually outmaneuvered by Deng Xiaoping who rose to supreme power and were deprived of all their important government and Party posts in the early 1980s.