 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 . 
