The Eastern Himalayas has been home to three independent kingdoms since the 17thcentury, including the Kingdom of Bhutan, the Kingdom of Sikkim, and the Kingdom of Nepal. The Himalayan kingdoms served as buffer states between Imperial China and India. In the 19thcentury, Nepal, Sikkim, and Bhutan became protectorates of British India. The Anglo-Nepal Treaty of 1923 recognized Nepal's sovereignty. The treaty was recorded in the League of Nations. Bhutan's relations with British India were managed under the Treaty of Punakha of 1910. Sikkim's relations with British India were managed under the Treaty of Titalia of 1817 and the Treaty of Tumlong of 1861.
