July 25, 1967. 2:30 AM. The first paratroopers arrive in Detroit. 43 people are already dead, 324 injured, 7,231 arrested. The riots will continue for several more days, and there will be troops on the ground through July 30th.
Source:
Detroit troop strength map, 7/23/67, Ex HU 2, WHCF, Box 26, LBJ Library.