The Indus Valley civilization, one of the oldest in the world, dates back at least 5,000 years. Aryan tribes from the northwest infiltrated onto Indian lands about 1500 B.C.; their merger with the earlier Dravidian inhabitants created the classical Indian culture. Arab incursions starting in the 8th century and Turkish in the 12th were followed by those of European traders, beginning in the late 15th century. By the 19th century, Britain had assumed political control of virtually all Indian lands. Nonviolent resistance to British colonialism led by Mohandas Karamchand Gandhi and Jawaharlal Nehru brought independence in 1947.