Born into an elite princeling family, Yu ascended to head of North American operations for China's Ministry of State Security (MSS), during which time he acted as a double agent, passing information to the US Central Intelligence Agency (CIA).

They later divorced, and after the Marco Polo Bridge incident, Li fled to the Yun'an district of Guangdong Province where she first dated mutual friend and CCP spymaster Kang Sheng, and later, Mao Zedong, whom she married to become Jiang Qing, the inaugural first lady of the People's Republic of China and leader of the radical political alliance known as the Gang of Four.

Upon his return, he became the leader of a task force enforcing the One Strike and Three Anti's Campaign, which targeted people said to exhibit the 'counter-revolutionary' behaviors of 'graft and embezzlement', 'profiteering' and 'extravagance and waste.'

The task force was notable for arresting artist and writer Zhang Langlang [zh] (張郎郎), who was sentenced to death for criticizing the government, and accused of being a French spy.

[2][4] Despite not having participated in violent abuses that were trademarks of then-MPS spy chief Kang Sheng, Yu quickly rose through the ranks of the agency, moving to the fledgling Ministry of State Security soon after it split from the MPS in 1983.

[citation needed] As a member of the MPS sent down to the countryside during the Cultural Revolution, Yu was unable to protect his mother from degradation at the hands of Red Guards.

[2] As chief of counterintelligence within the North America Department of the MSS, Yu was sent to try to recruit the new arrival, but instead opted to use the imprimatur of the officially sanctioned contact with a member of the CIA to defect to the United States himself.

In the words of Roger Faligot, "thanks to Yu's perfidy, Larry had signed his own death certificate when he faithfully reported to his Chinese paylords that a new US agent was in town.

[8] In early 1982, Yu provided specific information regarding a Chinese mole: On February 6, 1982, the spy would arrive in Beijing on a Pan Am flight, stay in Room 553 of the Qianmen Hotel in Beijing, and call Zhu Entao, deputy director of the Foreign Affairs Bureau of the MPS, after which the spy will be appointed as a deputy bureau-level official.

Smith, head of the China Counterintelligence Team of the FBI, received a message from the CIA that said the U.S. Intelligence Community had been penetrated by a longstanding Chinese mole.

Smith gave the source the codename PLANESMAN, a term for the person who operates the diving plane, a control surface which determines the elevation and depth of a submarine.

He strolled around MSS headquarters, routinely photographing documents on desks, pulling files, and making inquiries, and being the son of those with influence, he benefited from special treatment.