During this campaign, the 21st suffered heavy casualties during the Battle of Spotsylvania and the Battle of Bethesda Church. In the latter engagement, the 21st acted as rear guard and bore the brunt of a fierce attack but held their position. Grant's Overland Campaign concluded with several assaults on Petersburg, Virginia, on June 15–18, 1864. The 21st again took considerable casualties during these attacks, particularly during the assault on June 17. Maj. Henry Richardson, commanding the 21st, was wounded in the thigh during the engagement and was shortly thereafter sent home. Now numbering less than 100 men, the regiment had been reduced to a tenth of its original size. Company A, by this time, had only three men on its active roster.