Following the 1962 Sino-Indian War, tensions continued to run high along the Himalayan border shared by India and China. Influenced by its previous defeat, the Indian Army raised a number of new units, nearly doubling their deployed forces along the disputed region. As a part of this military expansion, seven mountain divisions were raised to defend India's northern borders against any Chinese attack. Most of these divisions were not based near the border, save for the Chumbi Valley, where both Indian and Chinese troops are stationed on both sides at close range. Particularly at the Nathu La pass in the valley, alongside the Sikkim-Tibet border, the deployed Chinese and Indian forces are stationed about 20–30 meters apart, which is the closest of anywhere on the 4000 km Sino-Indian border. The border here is said to have remained "un-demarcated". Chinese held the northern shoulder of the pass, while the Indian Army held the southern shoulder. Two major parts of the pass, south and north of Nathu La, namely "Sebu La" and "Camel’s back," were held by the Indians. From 1963, small-scale clashes in the region were frequently reported in the press. On 16 September 1965, during the Indo-Pakistani War of 1965, China issued an ultimatum to India to vacate the Nathu La pass. However, GOC 17 mountain division's Major General, Sagat Singh, refused to do so, arguing that Nathu La was on the watershed which comprised the natural boundary.