In February 1864, the commander of the Union Department of the South, Maj. Gen. Quincy A. Gillmore, launched an expedition into Florida to secure Union enclaves, sever Rebel supply routes, and recruit black soldiers. Brig. Gen. Truman Seymour moved his 5,500-man force from Jacksonville deep into the state, meeting little resistance. On February 20th, as he advanced toward Lake City, he approached Brig. Gen. Joseph Finegan’s 5,000 Confederates entrenched in an open pine woods near Olustee. Finegan send forward one infantry brigade to meet Seymour’s advance units. The Union forces attacked but were repulsed. Seymour, believing he was attacking Florida militia units, sent in his forces piecemeal. The battle raged, and as Finegan committed the last of his reserves, the Union line broke and began to retreat. Finegan did not fully exploit the withdrawal, however, some of his men attempted to engage the rear element of Seymour's forces just before nightfall, and were repulsed by elements of the 54th Massachusetts Volunteer Infantry Regiment and the 35th United States Colored Troops. According to some Confederate memoirs and letters, Confederate troops killed most of the wounded and captured black Union soldiers. The Union losses caused Northern authorities to question the necessity of further Union involvement in the militarily insignificant state of Florida.