Meet Sonam Dorje, who lived in Chinese custody for 21 days

Sonam Dorje is a retired CRPF personnel who was captured by the Chinese forces in 1959 on the grounds of espinoage. After spending 21 days in custody of the Chinese soldiers, Sonam was released. How did a CRPF personnel end up in Chinese custody? How was his release secured? Why

source https://news.abplive.com/videos/news/india-meet-sonam-dorje-who-lived-in-chinese-custody-for-21-days-1269871