Shortly after the Union Army of the Southwest entered Arkansas in February 1862, three divisions moved to Osage Springs in an attempt to trap Confederate troops in their winter quarters. The attempt failed, but the soldiers established Camp Halleck, which stretched five miles, and monitored Confederate activity. As skirmishing increased, Union Gen. Samuel Curtis requested reinforcements, but the request was declined. On March 1, 1862, in response to Confederate movements, Curtis moved the men from Camp Halleck to build fortifications on high ground on Pea Ridge.