The Third Colorado Cavalry was formed in the mid-1860s when increased traffic on the United States emigrant trails and settler encroachment resulted in numerous attacks against them by the Cheyenne and Arapaho. The Hungate massacre and the display in Denver of mutilated victims raised political pressure for the government to protect its people. Governor John Evans sought and gained authorization from the War Department in Washington to found the Third. More a militia than a military unit, the "Bloodless Third" was composed of "100-daysers," that is, volunteers who signed on for 100 days to fight against the Indians. (Its nickname came from its lack of battle experience.)