High Quality Content by WIKIPEDIA articles! The Battle of Wavre was the final major military action of the Hundred Days campaign and the Napoleonic Wars. It was fought on 18-19 June 1815 between the Prussian rearguard under the command of General Johann von Thielmann and three corps of the French army under the command of Marshal Grouchy. A blocking action, this battle kept 33,000 French solders off the Battlefield of Waterloo. This battle helped the Allied forces win the Battle of Waterloo.