With the outbreak of the Civil War in the United States, a number of ethnically-oriented militia groups responded to President Lincoln's call for volunteers to preserve the union. One such unit to volunteer was a predominantly German-American unit known as the Citizens Corps of Milwaukee. On 25 and 27 April 1861, the unit officers, William Lindwurm, Frederick Schumacher, and Werner Von Bachelle were commissioned captain, first lieutenant, and second lieutenant of the company, respectively. By 10 May 1861, the company was officially mustered into the evolving 6th Wisconsin Regiment as Company F, bringing the total of German-Americans in the Union Army to almost thirty-six thousand.

On 16 July 1861, the 6th Wisconsin Volunteers departed for Washington, D.C. Here, the regiment was brigaded with the Union Army's 2d and 7th Wisconsin Regiments and the 19th from Indiana, under Brig. Gen. John Gibbon. The brigade, in 1862, achieved increased efficiency and military prowess and a distinctive uniform that resulted in the nickname "Black Hat Brigade" from fellow Union soldiers. Following the brigade's determined assault upon the heights at Turner's Gap at South Mountain, Maryland, Gibbon's brigade won a new title, "The Iron Brigade of the West". Three days later, the unit proved its worth once again by bravely assaulting Lee's forces in one of the bloodiest battles of the war.