After being promoted to Captain of the Chicago Mercantile Battery on February 28, 1863, Patrick White and his new troops participated in several Union successes prior to Vicksburg. The Battery actively contributed to victories at the battles of Port Gibson, Big Black River, and Champion Hill. On May 22, 1863, General Ulysses S. Grant conducted his first major assault against the Confederate defenses of Vicksburg, Mississippi. In the midst of Grant's en echelon attack, General Andrew Jackson Smith sought an artillery commander to take on a particularly dangerous assignment. White accepted this request to transport a six-pound cannon down a steep hill and then up another to fire point blank into a Rebel stronghold. The Confederate target was the Second Texas Lunette, a fort from which the Confederate soldiers were tenaciously fighting to prevent Smith's men from obtaining access to Hawkins Ferry Road, one of the major entrances into Vicksburg. White and his small band of artillerymen were joined by some infantrymen from the 23 Wisconsin who helped them to pull their cannon through the ravine up to the Confederate fort. For his valor at the siege of Vicksburg, White was awarded the Medal of Honor.
