1962 War:

Relations of India with China turned soure in 1962 when Chinese forces attacked the Thagla ridge and dislodged troops, which was initial spark for ensuing massive attack. In October 1962, the Chinese army launched a massive attack and overran India posts in the eastern sector in NEFA (now Arunachal). India army commander in NEFA fled without resistance and left behind open door for Chinese personnel to attack India. In western sector, Chinese captured 13 posts in the Galwan Valley and the Chushul airstrip was threatened. India was apprehensive of such move by China and sought American and British help later, However Chinese themselves declared a unilateral withdrawal, nonetheless the relations between the two nations were strained for years to come after the war.