Upon arriving in Vincennes on February 23, 1779, Clark's men, tired, cold, wet, and starving from the lack of food on the march, were provided for by the local French inhabitants who greeted the Americans warmly. That same evening, Clark's men surrounded the fort and began to fire on it. Clark knew it would still be tricky for his small force to intimidate Hamilton into surrendering, so he employed several different strategies to strengthen his position. He gave his men orders to make noise and to fire as often and as much as they could in order to give the illusion of a much greater force. Clark also gave orders that every time the cannon ports opened in an attempt to fire a round, American riflemen would be trained on those openings and would fire immediately and heavily. The British had great difficulty in successfully firing cannon shots during the battle. To further unnerve the British, Clark directed some of his men to the riverside of the fort to begin tunneling the 30 feet to the fort and its black powder stores.
In one of Clark's most controversial attempts to intimidate the occupants of the fort, he intercepted some Indian allies of the British who were returning to the fort unaware of Clark's attack. Clark saw an advantage to be taken and decided to have the Indians executed within view of the fort. This served as a symbol both to other Indians that the British could no longer protect them, and to Hamilton that his troops might receive the same treatment if Clark was forced to storm the fort.
Hamilton was greatly influenced by Clark's military tactics, and surrendered the fort on February 25. After only a two day battle, with no confirmed losses either inside the fort or among Clark's men, the Battle of Fort Sackville was over.