But the French, besides losing about 15,000 men, together with a column of prisoners more than 2000 in number, began now to be disturbed by the operations of the Prussians on their right flank; and the secret of the Duke of Wellington was disclosing itself by its consequences. Blucher, faithful to his engagement, had, early in the morning, put in motion Bulow's division, which had not been engaged at Ligny, to communicate with the English army, and operate a diversion on the right flank and rear of the French. But although there were only about twelve or fourteen miles between Wavre and the field of Waterloo, yet the march was, by unavoidable circumstances, much delayed. The rugged face of the country, together with the state of the roads, so often referred to, offered the most serious obstacles to the progress of the Prussians, especially as they moved with an unusually large train of artillery. A fire, also, which broke out in Wavre, on the morning of the 18th, prevented Bulow's corps from marching through that town, and obliged them to pursue a circuitous and inconvenient route. After traversing, with great difficulty, the cross-roads by Chapelle Lambert, Bulow, with the 4th Prussian corps, who had been expected by the Duke of Wellington about eleven o'clock, announced his arrival by a distant fire, about half-past four. The first Prussian corps, following the same route with Bulow, was yet later in coming up. The second division made a lateral movement in the same direction as the fourth and first, but by the hamlet of Ohain, nearer to the English flank. The Emperor instantly opposed to Bulow, who appeared long before the others, the 6th French corps, which he had kept in reserve for that service; and, as only the advanced guard was come up, they succeeded in keeping the Prussians in check for the moment. The first and second Prussian corps appeared on the field still later than the fourth. The third corps had put themselves in motion to follow in the same direction, when they were furiously attacked by the French under Maréchal Grouchy, who, as already stated, was detached to engage the attention of Blucher, whose whole force he believed he had before him. Instead of being surprised, as an ordinary general might have been, with this attack upon his rear, Blucher contented himself with sending back orders to Thielman, who commanded the third corps, to defend himself as well as he could upon the line of the Dyle. In the meantime, without weakening the army under his own command, by detaching any part of it to support Thielman, the veteran rather hastened than suspended his march towards the field of battle, where he was aware that the war was likely to be decided in a manner so complete, as would leave victory or defeat on every other point a matter of subordinate consideration.