Eastern theatre
Chinese troops launched an attack on the southern banks of the Namka Chu River on 20 October.[39] The Indian forces were undermanned, with only an understrength battalion to support them, while the Chinese troops had three regiments positioned on the north side of the river.[39] The Indians expected Chinese forces to cross via one of five bridges over the river and defended those crossings.[8] However, the PLA bypassed the defenders by crossing the shallow October river instead. They formed up into battalions on the Indian-held south side of the river under cover of darkness, with each battalion assigned against a separate group of Rajputs.[39]
At 5:14 am, Chinese mortar fire began attacking the Indian positions. Simultaneously, the Chinese cut the Indian telephone lines, preventing the defenders from making contact with their headquarters. At about 6:30 am, the Chinese infantry launched a surprise attack from the rear and forced the Indians to leave their trenches.[39]
The Chinese troops overwhelmed the Indians in a series of flanking manoeuvres south of the McMahon Line and prompted their withdrawal from Namka Chu.[39] Fearful of continued losses, Indian troops escaped into Bhutan. Chinese forces respected the border and did not pursue.[8] Chinese forces now held all of the territory that was under dispute at the time of the Thag La confrontation, but they continued to advance into the rest of NEFA.[39]
On 22 October, at 12:15 am, PLA mortars fired on Walong, on the McMahon line.[45] Flares launched by Indian troops the next day revealed numerous Chinese milling around the valley.[45] The Indians tried to use their mortars against the Chinese but the PLA responded by lighting a bushfire, causing confusion amongst the Indians. Some 400 Chinese troops attacked the Indian position. The initial Chinese assault was halted by accurate Indian mortar fire. The Chinese were then reinforced and launched a second assault. The Indians managed to hold them back for four hours, but the Chinese used sheer weight of numbers to break through. Most Indian forces to withdraw to established positions in Walong, while a company supported by mortars and medium machine guns remained to cover the retreat.[45]
On the morning 23 October, the Indians discovered a Chinese force gathered in a cramped pass and opened fire with mortars and machine guns, leading to heavy fighting. About 200 Chinese soldiers were killed and wounded in this action. Nine Indian soldiers were also killed. The fighting continued well into the afternoon, until the company was ordered to withdraw. Meanwhile, the 4th Sikhs made contact with the Chinese and subjected them to withering mortar and machine gun fire as the Chinese set off a brushfire and attempted to sneak forward. Sepoy Piara Singh tried to douse the fire while fighting the enemy, but died after he was wounded and refused to be evacuated.
Elsewhere, Chinese troops were launched a three-pronged attack on Tawang, which the Indians evacuated without any resistance.[8]
Over the following days, there were clashes between Indian and Chinese patrols at Walong as the Chinese rushed in reinforcements. On 25 October, the Chinese made a probe, which was met with resistance from the 4th Sikhs. As some Chinese soldiers began to close in, Sepoy Kewal Singh charged them with his bayonet and killed a few of them in hand-to-hand combat, but he himself was killed. The following day, a patrol from the 4th Sikhs was encircled, and after being unable to break the encirclement, an Indian unit sneaked in and attacked the Chinese flank, allowing the Sikhs to break free.[45]
Western theater
On the Aksai Chin front, China already controlled most of the disputed territory. Chinese forces quickly swept the region of any remaining Indian troops.[46] Late on 19 October, Chinese troops launched a number of attacks throughout the western theatre.[9] By 22 October, all posts north of Chushul had been cleared.[9]
On 20 October, the Chinese easily took the Chip Chap Valley, Galwan Valley, and Pangong Lake.[47] Many outposts and garrisons along the Western front were unable to defend against the surrounding Chinese troops. Most Indian troops positioned in these posts offered resistance but were either killed or taken prisoner. Indian support for these outposts was not forthcoming, as evidenced by the Galwan post, which had been surrounded by enemy forces in August, but no attempt made to relieve the besieged garrison. Following the 20 October attack, nothing was heard from Galwan.[8]
On 24 October, Indian forces fought hard hold the Rezang La Ridge, in order to prevent a nearby airstrip from falling to the Chinese .[48]
After realising the magnitude of the attack, the Indian Western Command withdrew many of the isolated outposts to the south-east. Daulet Beg Oldi was also evacuated, but it was south of the Chinese claim line and was not approached by Chinese forces. Indian troops were withdrawn in order to consolidate and regroup in the event that China probed south of their claim line.[8]
