evidence: In the central sector, new check-posts were established by the Indo-Tibetan Border Force in the previously disputed areas. This was supposedly ordered by Nehru in a secret memorandum issued in July 1954 (Gupta 1974: 765). The North-East Frontier Agency (NEFA) was also established. In 1955, India occupied Pulam Sumda (Bo lin san duo), which is one of the ten trade markets that the Chinese government had agreed to open in the Ngari Prefecture of Tibet in accordance with the 1954 Sino-Indian Agreement. In 1957, India occupied Shipki La (Shi pu qi shankou) in the central sector which is one of the four important passageways from India to Tibet in the central sector. In view of the fact that China was busy with the Korean War in the early 1950s, and considering the blossoming of China–India friendship, Beijing protested over these various Indian actions but maintained the peace. The Chinese side reiterated China’s position on different occasions, namely, that the border had never been formally demarcated.5 However, there continued to be a cognitive gap between China and India on this issue.