George Rogers Clark's capture of Kaskaskia in July, 1778, doomed British control of the Illinois country. The occupation of Kaskaskia was the first step in Clark's plan to capture the western headquarters of the British at Detroit. Under authorization from Virginia, Clark raised about 175 troops. They arrived near Kaskaskia during the night of July 4-5, after a grueling two-months' journey of more than one thousand miles. Most of the British had been withdrawn, and Kaskaskia fell without gunfire. Clark's victory and the capture of the other frontier posts opened the Illinois country to westward expansion.