From: The Second Great Migration

"The Detroit 'hate' riots erupted in June 1943 at Belle Island, a popular segregated beach. On June 20, 1943, fights broke out between groups of white and African-American youths. News of the altercation spread, and by that night a full-scale riot had erupted. The Detroit police force was unable to quell the disturbance; Detroit Mayor Edward Jefferies requested assistance, but federal authorities were reluctant to intervene. 

"The violence escalated, and President Franklin D. Roosevelt ordered military police and infantry regiments to disperse rioters late on the second night of the riots. Order was restored, but in a day and a half of rioting, 25 African Americans and 9 whites were killed, almost 700 people were injured, and 1,893 people were arrested . . . "