Oklahoma in the Great War. On April 6, 1917, the United States entered World War I. As the country prepared for war, the state of Oklahoma answered the call. Thousands of men, including Native Americans who did not have American citizenship, entered the service prepared to sacrifice their lives while men and women on the home-front dedicated themselves to supporting the war effort. Like many other states, Oklahoma was hampered by overzealous Councils of Defense and the devastating Flu Epidemic, overcame those challenges to provide a unified front. Author illuminates the fascinating history of the state by bringing together little-known stories from all over Oklahoma.