The Sino-Indian War was fought during his term, in which the Indian Army fared poorly.

Thapar was distantly related to the Indian Prime Minister Jawaharlal Nehru through his wife.

[10] He spent the next year attached to a British Army battalion stationed in India.

[13] He was appointed as assistant military secretary in 1945, and commanded the 1st Battalion of the 1st Punjab Regiment in Indonesia in 1946.

He served as the Chief of the General Staff for a few months and later as Military Secretary until August 1949.

[14] On 1 January 1950, Thapar was promoted to substantive major-general, and was given command of an infantry division on 10 April.

After resigning from the army, he was appointed as Indian Ambassador to Afghanistan from August 1964 to January 1969.