[2] The regiment was composed almost entirely of immigrant volunteers: Poles, Germans, Danes, Italians, Russians, and Frenchmen, most of whom were recruited in New York City in 1861.

[3] In August 1861, Włodzimierz Krzyżanowski, a Polish officer who had fought in the Greater Poland Uprising (1848), was authorized by United States Secretary of War Simon Cameron to recruit a regiment.

[3] The regiment left Washington, crossed the Potomac River on November 13, 1861, into Virginia, and marched to Hunter's Crossroads, where it joined its division.

The division marched through Virginia from Hunter's Crossroads, to Burke, Fairfax Court House, Manassas Junction, Warrenton, Salem, Paris, Millwood, and arrived at Winchester, on April 20.

[3] 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 100 yards (90 m), their gallantry on the battlefield was noted in Bohlen's official report.

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.

Under command of Major William Henkel, the regiment actively engaged in the Second Battle of Bull Run, August 29–30, and suffered 57 casualties: 14 killed, 32 wounded (including those mortally), and 11 missing.

Schurz's regiments held the ground for a half hour or more, and then finding that the Confederate overlapped their line on either flank fell back.

The regiment was not engaged during the succeeding days of the battle, after which it recrossed the Rappahannock River with the army, and, marching in a rain storm, accompanied XI Corps back to the vacant Stafford Courthouse camp, which was reoccupied by the soldiers.

After marching about 5 miles (8.0 km), and not seeing any signs of Confederates, Koenig halted his detachment and gave his men an opportunity for rest and sleep.

In the meantime the remainder of the regiment, composed of two companies, engaged in the battle of the First Day on the north side of the town, and had fallen back through the streets to Cemetery Hill, with the rest of the army.

Confederate artillery barrage against the position of XI Corps, the exploding fragments dealing death and wounds throughout the ranks of every regiment.

[6] At dusk Harry T. Hays's Louisiana Brigade (Louisiana Tigers) and Robert Hoke's North Carolina Brigade assaulted the Union position on East Cemetery Hill, and attaining a temporary success charged up the slope and through the line of cannon in Captain Michael Wiedrich's Battery I, New York Light Artillery, driving the gun crews from their weapons.

As another attack was momentarily expected, the regiment was ordered to remain, one of its companies, under Lieutenant Schwartz, being sent out as skirmishers to ascertain the direction in which the Confederates had moved.

[6] On the morning of July 3 the regiment moved to the right of the Baltimore Pike leading into Gettysburg, and into a position behind a stone fence on the left of Wiedrich's Battery.