Unable to reach political accommodation on disputed territory along the 3,225-kilometer-long Himalayan border, the Chinese attacked India on October 20, 1962. At the time, nine divisions from the eastern and western commands were deployed along the Himalayan border with China. None of these divisions was up to its full troop strength, and all were short of artillery, tanks, equipment, and even adequate articles of clothing.

In Ladakh the Chinese attacked south of the Karakoram Pass at the northwest end of the Aksai Chin Plateau and in the Pangong Lake area about 160 kilometers to the southeast. The defending Indian forces were easily ejected from their posts in the area of the Karakoram Pass and from most posts near Pangong Lake. However, they put up spirited resistance at the key posts of Daulat Beg Oldi (near the entrance to the pass) and Chushul (located immediately south of Pangong Lake and at the head of the vital supply road to Leh, a major town and location of an air force base in Ladakh). Other Chinese forces attacked near Demchok (about 160 kilometers southeast of Chusul) and rapidly overran the Demchok and the Jara La posts.

In the eastern sector, in Assam, the Chinese forces advanced easily despite Indian efforts at resistance. On the first day of the fighting, Indian forces stationed at the Tsang Le post on the northern side of the Namka Chu, the Khinzemane post, and near Dhola were overrun. On the western side of the North-East Frontier Agency, Tsang Dar fell on October 22, Bum La on October 23, and Tawang, the headquarters of the Seventh Infantry Brigade, on October 24. The Chinese made an offer to negotiate on October 24. The Indian government promptly rejected this offer.

With a lull in the fighting, the Indian military desperately sought to regroup its forces. Specifically, the army attempted to strengthen its defensive positions in the North-East Frontier Agency and Ladakh and to prepare against possible Chinese attacks through Sikkim and Bhutan. Army units were moved from Calcutta, Bihar, Nagaland, and Punjab to guard the northern frontiers of West Bengal and Assam. Three brigades were hastily positioned in the western part of the North-East Frontier Agency, and two other brigades were moved into Sikkim and near the West Bengal border with Bhutan to face the Chinese. Light Stuart tanks were drawn from the Eastern Command headquarters at Calcutta to bolster these deployments.

In the western sector, a divisional organization was established in Leh; several battalions of infantry, a battery of twenty-five-pounder guns, and two troops of AMX light tanks were airlifted into the Chushul area from Punjab. On November 4, the Indian military decided that the post at Daulat Beg Oldi was untenable, and its defenders were withdrawn over the 5,300-meter-high Sasar Brangsa Pass to a more defensible position.

The reinforcements and redeployments in Ladakh proved sufficient to defend the Chushul perimeter despite repeated Chinese attacks. However, the more remote posts at Rezang La and Gurung Hill and the four posts at Spanggur Lake area fell to the Chinese.

In the North-East Frontier Agency, the situation proved to be quite different. Indian forces counterattacked on November 13 and captured a hill northwest of the town of Walong. Concerted Chinese attacks dislodged them from this hard-won position, and the nearby garrison had to retreat down the Lohit Valley.

In another important section of the eastern sector, the Kameng Frontier Division, six Chinese brigades attacked across the Tawang Chu near Jang and advanced some sixteen kilometers to the southeast to attack Indian positions at Nurang, near Se La, on November 17. Despite the Indian attempt to regroup their forces at Se La, the Chinese continued their onslaught, wiping out virtually all Indian resistance in Kameng. By November 18, the Chinese had penetrated close to the outskirts of Tezpur, Assam, a major frontier town nearly fifty kilometers from the Assam-North-East Frontier Agency border.

The Chinese did not advance farther and on November 21 declared a unilateral cease-fire. They had accomplished all of their territorial objectives, and any attempt to press farther into the plains of Assam would have stretched their logistical capabilities and their lines of communication to a breaking point. By the time the fighting stopped, each side had lost 500 troops.

The fighting war was over, but a new diplomatic war had begun. After more than thirty years of border tension and stalemate, high-level bilateral talks were held in New Delhi starting in February 1994 to foster "confidence-building measures" between the defense forces of India and China, and a new period of better relations began.