Often confused for the 1st Florida Infantry Regiment that served at Pensacola in 1861 and early 1862, this was actually a battalion of infantry organized in early 1862 under the command of Major T.A. McDonnell. The battalion remained an independent unit until late summer of 1862. Many of its men had earlier served in the 1st Florida Infantry Regiment and most went on to serve in other regiments, including yet another 1st Florida Infantry Regiment that was organized in August of 1862.
It is a bit confusion but basically there was a 1st Florida Regiment in 1861, followed by a 1st Florida Battalion in early 1862 followed by another 1st Florida Regiment in late summer of 1862.
At the Battle of Shiloh, the 1st Florida Battalion was part of Patton Anderson's 2nd Brigade of General Daniel Ruggles' 1st Division of General Braxton Bragg's Second Corps. As it pressed forward with the rest of Bragg's Corps, the 1st Florida came under heavy fire. Major McDonnell fell mortally wounded early in the fighting and Captain W.G. Poole assumed command.