Hobart rejoined the 21st Regiment in April 1864 at Lookout Mountain, Tennessee, where they had been stationed since the retreat from Chikamauga. The Regiment marched from Lookout Mountain on May 2 to join the Atlanta Campaign, attached to General William Tecumseh Sherman's army. At the Battle of Rocky Face Ridge, the 21st joined in the flanking maneuver that forced the Confederates to abandon their position and fall back toward Resaca. At the Battle of Resaca, the 21st was again engaged in heavy fighting, as their brigade was ordered to assault the enemy fortifications. A few days later, at the Battle of Dallas, the regiment held a defensive position under heavy fire for six days. They received the compliments of their brigade commander, General William Carlin, for their fortitude and gallantry.