In February 1864, Union forces landed in Jacksonville and launched a major expedition westward into the interior of the state. Union objectives included
cutting off Confederate supply lines, locating recruits for black Union regiments, and establishing a pro-Union government in east Florida. The Union expedition was commanded by Brigadier General Truman Seymour. To counter this move, Confederate Brigadier General Joseph Finegan gathered southern troops sent from north Florida, southern Georgia, and South Carolina.
In the largest battle fought in Florida, approximately 5,500 Union troops clashed with a roughly equal number of Confederates at a point east of Lake City. For several hours in the afternoon of February 20, 1864, fighting raged in the pine woods near Olustee Station and Ocean Pond. Both commanders committed their forces only a few units at a time; however, the Confederates established a more effective position. As a result, the federal units directly engaged in the battle faced a relatively larger number of southern troops. Three regiments of African American troops fought in the battle and suffered heavy casualties. The Confederates held their ground and inflicted a stinging defeat on the Union forces. As darkness approached, the Union troops began their retreat to Jacksonville.
For its size (approximately 11,000 soldiers altogether), the battle was one of the bloodiest clashes of the war, with 1,861 Union casualties and 946 Confederate casualties. The Confederate victory helped keep the interior of the state under the South's control.