Two Union columns, one under Col. J.B. Plummer and another under Col. William P. Carlin, advanced on Fredericktown to overtake Brig. Gen. M. Jeff Thompson and his men. On the morning of October 21, Thompson's force left Fredericktown headed south. About twelve miles out, Thompson left his supply train in a secure position and returned toward Fredericktown. He then learned that Union forces had occupied Fredericktown, so Thompson spent the morning attempting to discern the enemy numbers and disposition. Unable to do so, he attacked anyway, around noon. Plummer, with his force and a detachment of Col. William P. Carlin's troops, met the Rebel forces outside town and a two-hour fight ensued. Overwhelming Union forces took their toll, and Thompson's men retreated. Union cavalry pursued. Fredericktown cemented Union control of southeastern Missouri.