There were still not enough Union troops to convince Frazer to surrender. An ineffectual exchange of artillery followed but that evening Union soldier captured Gap Springs, the Confederate water supply.[3] On September 8 Burnside personally left Knoxville with a brigade under Colonel Samuel A. Gilbert and marched 60 miles in just over a day.[4] Meanwhile, both DeCourcy and Shackelford sent messages demanding surrender. Attempting to buy time, Frazer met with the two Union commanders separately, but rejected surrender demands from both.