The Dalai Lama’s visit to Tawang has not been taken kindly by China, as they consider Tawang to be part of southern Tibet, and, therefore, a part of China. India, on the other hand, has repudiated their claim, citing a treaty signed by the British and Tibetan representatives, popularly called the “Simla treaty,” under which Arunachal Pradesh was declared to be part of India. China had rejected the treaty on the grounds that the then-Tibetan government was not representing a sovereign country and had illegally entered into an agreement with the British. Arunachal Pradesh became one of the main focal points that led to the Sino-Indian war in 1962, where the Chinese entered 45 kilometers inside Arunachal Pradesh but vacated to avoid international pressure. However, they did manage to occupy over 30,000 square kilometers in the Aksai Chin area, which they have refused to vacate. Aksai Chin and Arunachal Pradesh continue to be a major thorn in Sino-India relations. In spite of holding 16 rounds of border talks, no agreement is in sight.[Source]