Manipur () is a state in northeastern India, with the city of Imphal as its capital. The state is sometimes referred to by alternative names such as Kangleipak and Meeteileipak. It is bounded by Nagaland to the north, Mizoram to the south, and Assam to the west; Burma lies to its east. The state covers an area of . Its people include the Nagas, Meeteis, Kuki, Hmar,Pangal, Gorkhali and Bishnupriya Manipuri, who speak different types of Sino-Tibetan languages. Manipur has been at the crossroads of Asian economic and cultural exchange for more than 2,500 years. It has long connected the Indian subcontinent to Southeast Asia, enabling migration of people, cultures and religions. It has also witnessed many wars, including fighting during World War II. The Kingdom of Manipur was one of the princely states of British India. Between 1917 and 1939, the people of Manipur pressed for their rights against the British Raj. By late 1930s, the princely state of Manipur negotiated with the British administration its preference to be part of India, rather than Burma (now Myanmar). These negotiations were cut short with the outbreak of World War II. On 21st September 1949, Maharaja Budhachandra signed a Treaty of Accession merging the kingdom into India; this merger is disputed by various groups in Manipur as having been completed without consensus and under duress. The dispute and different visions for future has led to a 50-year insurgency in the state for independence from India, as well as to violence between different ethnic groups within the state. Over 2010–2013, the militant insurgency was responsible for the violent death of about 1 civilian per 100,000 people, each year. The world’s average annual death rate from intentional violence has been 7.9 per 100,000 people. The Meetei ethnic group, constitute a plurality of the population ethnic group. 27% of the total population. Tribal people constitute 30% of the state population. There are many other tribes, practicing a variety of religions. The language of Meetei people, Meitei (or Manipuri), is the lingua franca in Manipur. Manipur is primarily an agrarian economy, with significant hydroelectric power generation potential. It is connected by daily flights through Imphal airport, the second largest airport in northeastern India. Manipur is credited with introducing Polo to Europe.