Why did the US authorities prevent Qian Xuesen from returning to China?

The fact is that the American authorities did not stop Qian Xuesen from returning to China.

1950, the American authorities revoked Qian Xuesen's confidential work permit, which was obviously humiliating. Qian Xuesen's first reaction was to return to China. But the American government stopped him and tried to leave the American secrets he knew in the United States. Later, Qian Xuesen and the US government changed their minds.

Qian Xuesen proposed to become an American citizen in order to obtain a confidential work permit again, but the US Immigration Bureau wanted to expel him from the country, while some anti-* * agencies in the United States asked the Immigration Bureau to keep Qian Xuesen.

For this matter, several forces fought for several years, until 1955, the US Immigration Service won. Qian Xuesen returned to China in this way.