In May 1815 General , commander of the Prussian II Corps, was sent home after protesting against the rough treatment of revolting Saxon units. Pirch replaced him as commander of the corps. At the beginning of Waterloo campaign, II Corps under Pirch's command numbered 30,000 men and officers. The corps was heavily engaged in the Battle of Ligny on 16 June, suffering about 6,000 casualties and similar number of deserters. On June 18 Pirch's Corps set off from Wavre following after Bülow's IV Corps, eventually reaching Napoleon's flank at the Battle of Waterloo. Pirch's leading unit, 5th Infantry Brigade, joined the heavy fighting over Plancenoit village. Only part of Pirch's II Corps saw action in the battle, with a significant portion being bogged down in muddy country roads. After the battle Pirch was tasked with stopping the retreat of Grouchy's force at Wavre, but his assault on Namur failed due to the exhaustion of his troops and lack of reconnaissance. After Waterloo Pirch handed over the command of II Corps to Prince Augustus of Prussia.