What caused the Trail of Tears?

The Trail of Tears was the name given to the forced relocation of Native-American tribes from their ancestral homelands in the Southeastern United States to west of the Mississippi. The impetus for this notorious policy was the Indian Removal Act of 1830. Prior to this, successive American governments had tolerated the existence of Native-American tribes in the Southern states so long as they could be culturally assimilated. However, President Andrew Jackson abandoned this relatively benign policy in favor of forced removal.
Acculturation was of no consequence to Jackson; as far as he and other Southerners were concerned, Native-Americans were occupying valuable tracts of land that they, the Southerners, wanted for themselves. As the numerous tribes were unlikely to give up their ancestral homelands without a fight, only a military solution was felt to be appropriate to resolve the matter.
Strange as it may seem, Jackson genuinely believed that forced resettlement was a humane policy, one that would prevent tribes such as the Cherokee from being wiped out altogether. In actual fact, however, the Indian Removal Act, and the Trail of Tears to which it led, involved human suffering on an appalling scale. It has been estimated that something like 4,000 men, women, and children died of cold, hunger, and disease on their forced march to the West.