The left column advanced from Solre-sur-Sambre, by Thuin, upon Marchienne-au-Pont; the centre from Beaumont, by Ham-sur-Heure, upon Charleroi; and the right column from Philippeville, by Gerpinnes, upon Châtelet. At approximately 03:30 in the morning, the head of the left column came in contact with Prussian troops in front of Lobbes, firing upon, and driving in, the pickets of the 2nd Battalion of the 1st Regiment of Westphalian Landwehr, commanded by Captain von Gillhausen. This officer was aware that French troops had assembled in great force in his front the night before, and intended to attack him in the morning. He had posted his battalion carefully, so as to afford it every advantage from the hilly and intersected ground it occupied. However the French, inclined more to their right, and joined other troops advancing along the road to Thuin, which lay on his left. Shortly after they drove back an advanced cavalry vedette; and, at 04:30 commenced firing four guns on the outpost at Maladrie, about in front of Thuin. This cannonade announced the opening of the campaign by the French, and was heard by the Prussian troops forming the left wing of Steinmetz's Brigade. However the sound didn't carry well in the extremely thick and heavy air, and because of this the greater portion of the right wing of the brigade was unaware of the French advance for some time. The firing, was distinctly heard at Charleroi, and Zieten—who, by the reports which he had forwarded on 14 June to Blücher and Wellington, had fully prepared these commanders to expect an attack—lost no time in informing Blücher and Wellington that hostilities had commenced. Shortly before 05:00, he despatched "Courier Jäger" to their respective headquarters, Namur (Blücher) and Brussels (Wellington). He informed them that since 04:30, he had heard several cannon shots fired in his front, and at the time he was writing the fire of musketry also, but that he had not yet received any report from his outposts. To Blücher he also intimated that he should direct the whole Corps to fall back into position, and should it become absolutely necessary to concentrate at Fleurus. Zieten's report to Wellington arrived in Brussels at 09:00; that to Blücher reached Namur between 08:00 and 09:00 on 15 June.