The British flag would not be raised above Fort Sackville on the morning of February 25, 1779. British Lieutenant-Governor Henry Hamilton and his garrison marched out of the fort at 10 a.m. and surrendered to American Colonel George Rogers Clark.
The British dominated a large portion of the Trans-Appalachian frontier after the French and Indian War. The Proclamation of 1763 forbid the settlement of lands west of the Appalachian Mountains. From their posts north of the Ohio River, the British sent Indian war parties against those settlers who ignored the proclamation line, including those in Kentucky.
George Rogers Clark organized the Kentucky militia to defend against these raids. Clark was not content to wait for the attacks. He decided that a major offensive campaign was needed. He took his plan to Patrick Henry, governor of Virginia, and gained approval. Clark's plan was to lead a force of frontiersmen into the Illinois country and strike at the source of the Indian raids.
During the summer of 1778 Clark directed his army down the Ohio River then overland some 120 miles to capture the British posts at Kaskaskia and Cahokia along the Mississippi River, near St. Louis. Although under British rule after the French and Indian War, these posts were populated by French settlers who had no great affection for the British. Clark quickly gained their support. Father Pierre Gibault and Dr. Jean Laffont volunteered to travel to Vincennes on behalf of the Americans and soon that settlement also gave its support to Clark. The French at Detroit and other northern posts, however, maintained the outward support of the British.
By Aug. 6, British Lt. Gov. Henry Hamilton received news about the fall of the three outposts. With a mixed force of English soldiers; French volunteers and militia; and Indian warriors, he left Detroit intending to retake Fort Sackville in Vincennes. Capt. Leonard Helm was Clark's subordinate in charge at Vincennes. Having only a few men upon whom he could depend, the American captain had no hopes of defending the fort against the British-Indian army. Hamilton retook the fort on Dec. 17. Faced with this formidable array, the French settlers of Vincennes returned to their British allegiance.
Then Hamilton made a fateful decision. He allowed most of his force to return to their homes for the winter, this was common practice in 18th century warfare. His intended invasion of the Illinois country would be postponed. Hamilton planned to gather his forces in the spring and to attack Clark's Mississippi River posts. Victories there would pave the way for a joint effort with tribes from south of the Ohio River to drive all American settlers from the Trans-Appalachian frontier.
Unaware that the fort was in British hands, Francis Vigo, a merchant and supporter of the American cause, set out from his St. Louis home for Vincennes. As he approached the settlement, he was taken prisoner and was held for several days. His captors failed to realize Vigo's involvement with the Americans and Hamilton allowed him to leave. Vigo agreed to one condition: that on his way back to St. Louis, Vigo would do nothing that would harm the British cause. After reaching St. Louis and keeping his promise, Vigo immediately went to Clark 50 miles south in Kaskaskia. Vigo provided valuable information concerning the military situation in Vincennes while informing Clark of the British intent to attack in the spring.
Determined to capture Hamilton, Clark and his force of approximately 170 Americans and Frenchmen made an epic 18-day trek from Kaskaskia through the freezing floodwaters of the Illinois country. At times in icy water up to their shoulders, it was Clark's determined leadership that brought them through this incredible midwinter journey. They arrived in Vincennes after nightfall on Feb. 23, 1779. The French citizens, eager to again renounce the British, warmly greeted Clark's men, providing food and dry gunpowder. Hamilton's garrison now consisted of approximately 40 British soldiers and a similar number of French volunteers and militia from Detroit and Vincennes. These French troops were not enthusiastic to fire upon the enemy when they realized that the French inhabitants of the town again had embraced the Americans.
Clark's men surrounded the fort and gave the impression of having a much larger army. Flags sufficient for an army of 500 had been brought from Kaskaskia and now were unfurled and carried within view of the fort. The American soldiers, who were experienced woodsmen, could maintain a rate of fire that convinced the British that the army indeed was large in number. These woodsmen were armed with the famed long rifle. And their aim was accurate. To further unnerve the garrison, Clark ordered tunneling operations to begin from behind the riverbank a short distance from the fort. Such tunnels were used to plant explosive charges under fort walls or beneath powder magazines. Barricades were thrown up and entrenchments were dug to provide additional cover.
Contemplating his predicament with increasing foreboding, Hamilton became resigned to surrendering. The Englishman requested Clark meet with him at the nearby church, St. Francis Xavier Catholic Church. Hamilton attempted to obtain liberal conditions while Clark insisted upon unconditional surrender. After a lengthy and heated discussion they failed to agree upon acceptable terms and each commander returned to their respective posts. At this time, an event occurred which caused the British to realize what might be their fate if the Americans were forced to storm the fort. An Indian raiding party, sent out by Hamilton to attack American settlers along the Ohio River, returned to Vincennes. Their entrance came during a lull in the battle and they saw the British flag flying, as usual, from the fort. The unsuspecting warriors, gleefully yelling and firing their weapons in the air, realized their mistake too late. Several Indians were killed or wounded by the frontiersmen while others were captured.
In retaliation for Indian raids in which numerous men, women and children had been slaughtered, Clark ordered five of the captured warriors to be tomahawked in full view of the fort. The executions were intended to heighten the psychological pressure upon the British, while also illustrating to Indian observers that the redcoats no longer could protect those tribes who made war on the Americans.
Following this grim scene, the lieutenant governor reluctantly agreed to Clark's final terms which were just short of unconditional surrender. Hamilton described his thoughts at having to surrender. "The mortification, disappointment and indignation I felt, may possibly be conceived..." The defeated British army marched out of Fort Sackville and laid down their muskets before their victors. The surrender occurred 10 a.m., Thurs., Feb. 25, 1779. An American flag was raised above the fort and 13 cannon shots were discharged in celebration. An accident during the firings severely burned several men including American Capt. Joseph Bowman. Six months later he died and was buried in the church cemetery adjacent to the fort.
Although unable to achieve his ultimate objective of capturing Detroit, Clark successfully countered British and Indian moves during the remainder of the conflict. The young Virginian had prevented the British from achieving their goal of driving the Americans from the Trans- Appalachian frontier. As a result of Clark's brilliant military activities, the British ceded to the United States a vast area of land west of the Appalachian Mountains. That territory now includes the states of Ohio, Indiana, Illinois, Michigan, Wisconsin and the eastern portion of Minnesota.
The exact location of the fort is not known. It is believed that the fort was located on the present-day George Rogers Clark National Historical Park. Archaeological evidence suggests that the fort's front wall was roughly between the Clark Memorial and the Lincoln Memorial Bridge in Vincennes, Indiana.
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