Napoleon sent Grouchy to pursue a part of the retreating Prussian army under the command of General Johann von Thielmann. On 17 June, Grouchy was unable to close with the Prussians. Despite hearing the cannon sound from the nearby Battle of Waterloo, he decided to follow the Prussians along the route literally specified in his orders, issued by Napoleon via Marshal Soult, while the Prussian and British-Dutch armies united to crush Napoleon. He won a smart victory over the III Prussian Corps in the Battle of Wavre, on 18–19 June 1815, but it was then too late, as by the time this battle was over Napoleon had already lost at Waterloo.