The British expedition to Tibet began in December 1903 and lasted until September 1904. The expedition was effectively a temporary invasion by British Indian forces under the auspices of the Tibet Frontier Commission, whose purported mission was to establish diplomatic relations and resolve the dispute over the border between Tibet and Sikkim. In the nineteenth century, the British conquered Burma, Bhutan, and Sikkim, occupying the whole southern flank of Tibet, which remained the only Himalayan kingdom free of British influence.