The goals of the Corps of Discovery, whose cadre would be raised primarily from the U.S. military, was to explore the Louisiana Purchase, and establish trade and U.S. sovereignty over the native peoples along the Missouri River.
1992 was the 500th anniversary of the day Columbus came to america. But in 1992 it was changed from Columbus day to indigenous peoples day. That is what led to massive protests in 1992.
The greatest effect of the European intrusion into the Americas was to increase the Indian and mestizo population through intermarriage with the whites. The primary cause of the massive population decline among native Americans after the European arrival was not warfare but disease.