On approaching Gembloux, Thielemann learned that Bülow had posted the IV Corps about 3 miles in rear of Grembloux, upon the old Roman road; whereupon Major Weyrach, aide-de-camp to Prince Blücher, who had continued with Thielemann during the night of 16 June, set off to seek out Blücher, and to report to him the position and attendant circumstances of the III and IV Corps, He soon succeeded in discovering the Prussian headquarters at Mellery, and communicated the above important information to Gneisenau.