The regiment's first engagement occurred on June 8 at the Battle of Cross Keys, Virginia, in which Frémont's forces were defeated by a Confederate corps under command of Jackson. The regiment made a bayonet charge in which the Confederate line was driven back about , their gallantry on the battlefield was noted in Bohlen's official report. Captain Louis Schirmer, 2nd Independent Battery, New York Light Artillery, reported of the "great gallantry" with which the regiment supported his battery during some of the battle. The regiment suffered 29 casualties at Cross Keys: 7 killed, 18 wounded, and 4 missing. The Union forces pursued Jackson, were defeated on June 9 at the Battle of Port Republic, went down the Shenandoah Valley to Middletown, Virginia, where General Franz Sigel relieved Frémont of command. The regiment was assigned to the 2nd Brigade of Carl Schurz's Division, and Krzyżanowski was assigned command of the brigade.