The independence of Bhutan has endured for centuries and it has never been colonized in its history. Situated on the ancient Silk Road between Tibet, the Indian subcontinent and Southeast Asia, the Bhutanese state developed a distinct national identity based on Buddhism. Headed by a spiritual leader known as the Zhabdrung Rinpoche, the territory was composed of many fiefdoms and governed as a Buddhist theocracy. Following a civil war in the 19th century, the House of Wangchuck reunited the country and established relations with the British Empire. Bhutan fostered a strategic partnership with India during the rise of Chinese communism and has a disputed border with China. In 2008, Bhutan transitioned from an absolute monarchy to a constitutional monarchy and held the first election to the National Assembly of Bhutan. The National Assembly of Bhutan is part of the bicameral parliament of the Bhutanese democracy. The country's landscape ranges from lush subtropical plains in the south to the sub-alpine Himalayan mountains in the north, where there are peaks in excess of 7,000 metres (23,000 ft). Gangkhar Puensum is the highest peak in Bhutan, and it may also be the highest unclimbed mountain in the world.The wildlife of Bhutan is notable for its diversity.