movements At around 06:00 of 18 June 1815 Grouchy reported to Napoleon that the Prussians had left Tourinnes by marching all night. He further reported that he was moving on Wavre with all haste. At 10:00 Grouchy reported to Napoleon that the Prussian I, II, and—mistakenly—III Corps were marching in the direction of Brussels, and that Prussian officers were talking of joining Wellington to offer battle to the French army. His despatch included a Prussian requisition form by way of proof. He suggested that by attacking and standing at Wavre, he could block the Prussians from intervening against the rest of the French army. At 11:30, Grouchy and his corps commanders heard in the distance the noise from the Grand Battery as the Battle of Waterloo started. Grouchy's corps commanders, especially Gérard, suggested that they should "march to the sound of the guns." Grouchy, however, had written and verbal orders from Napoleon to march on Wavre and to engage the Prussians there, and knew that Marshal Ney had been taken to task by Napoleon two days earlier for not following orders at the Battle of Quatre Bras. Grouchy therefore declined to follow his subordinates' suggestion, pointing out that Napoleon had more than enough force to deal with Wellington. Minutes after this conversation, Exelmans reported strong Prussian positions at Wavre. At 13:00, elements of Exelmans' cavalry were in contact with the Prussian 14th Brigade’s rear guard. Further argument was ended by the arrival at 16:00 of another order from Napoleon, repeating the instruction to Grouchy to attack the Prussians before him. Prussian movements Blücher had ordered Thielmann to defend the position of Wavre in the event of Marshal Grouchy advancing in force, or, if otherwise, to follow the main Prussian army in the direction of Couture-Saint-Germain and the battlefield of Waterloo. Thielmann was on the point of leaving Wavre to march towards Couture-Saint-Germain when the French III Corps (Vandamme's) arrived in front of his position, at about 16:00, and the French artillery immediately opened a cannonade upon the Prussians. All the brigades (the 9th, 10th, 11th, and 12th) of the Prussian III Corps (Thielmann's), had, at that time, received the order to commence the general movement to the right (west). A detachment of only two battalions (the Fusilier Battalions of the 30th Regiment and of the 1st Kurmark Landwehr), under Colonel Zepelin, from the 9th Brigade, which had not yet crossed