Why did China take the initiative to retreat during the Sino-Indian border war?

Whether you can hibernate after recovery is the main problem. There is no danger to defend on the terrain, logistics supply can't keep up, local infrastructure is poor, and there is no mass base.

If you choose defense, you must invest a lot of money and manpower, establish a perfect defense system, establish a logistics system that knows the border from the southwest, and emigrate on a large scale, which is impossible at that time. Even if it is finished, it will take time. Think about how long it took us to build the Qinghai-Tibet Railway.