 The 21st , now numbering 425 men , crossed Bull Run on August 29 and discovered that Union forces had already engaged Jackson 's men in the Second Battle of Bull Run . Just after noon , the 21st 's brigade took up a position near the center of the Union lines . Over the course of the afternoon they witnessed several brigades advance into the woods in their front only to see them beaten back by the Confederates . Finally , the order came for Ferrero 's brigade , including the 21st , to advance , unsupported , into the woods . As the brigade stepped off , Brig. Gen. Reno ordered it to halt and personally protested the order to Maj. Gen. Pope . The order was rescinded and , according to Capt. Walcott of the 21st , " we thanked God that General Reno stood between us and General Pope . " 
