On August 18, 1864, the 21st's three-year enlistment came to an end. More than three-quarters of the remaining men chose to re-enlist. These men were consolidated into a battalion of three companies commanded by Capt. Orange S. Sampson. The day after their consolidation, the battalion participated in the Battle of Globe Tavern. The final engagement in which the remaining companies of the 21st participated as an independent unit was the Battle of Poplar Springs Church on September 30, 1864, during which the Union army attempted to extend its lines westward, further encircling Petersburg. Capt. Orange Sampson, commanding the 21st, was killed in this engagement.