On February 25, 1779, Fort Sackville is surrendered, marking the beginning of the end of British domination in America’s western frontier.

Eighteen days earlier, George Rogers Clark departed Kaskaskia on the Mississippi River with a force of approximately 170 men, including Kentucky militia and French volunteers. The party traveled over 200 miles of land covered by deep and icy flood water until they reached Fort Sackville at Vincennes (Indiana) on February 23, 1779. After brutally killing five captive British-allied Native Americans within view of the fort, Clark secured the surrender of the British garrison under Lieutenant-Governor Henry Hamilton at 10 a.m. on February 25.

Upon their arrival in Vincennes, French settlers, who had allied themselves with Hamilton when he took the fort in December, welcomed and provisioned Clark’s forces. Inside Fort Sackville, Hamilton had only 40 British soldiers and an equal number of mixed French volunteers—French settlers fought on both sides of the American Revolution—and militia from Detroit. The French portion of Hamilton’s force was reluctant to fight once they realized their compatriots had allied themselves with Clark.

Clark managed to make his 170 men seem more like 500 by unfurling flags suitable to a larger number of troops. The able woodsmen filling Clark’s ranks were able to fire at a rapid rate that reinforced Hamilton’s sense that he was surrounded by a substantial army. Meanwhile, Clark began tunneling under the fort with the intent of exploding the gunpowder stores within it. When a Native American raiding party attempted to return to the fort from the Ohio Valley, Clark’s men killed or captured all of them. The public tomahawk executions served upon five of the captives frightened the British as to their fate in Clark’s hands. Their subsequent surrender revealed British weakness to the area’s Native Americans, who realized they could no longer rely on the British to protect them from the Patriots.