As to the centre (the main body of the army), its cavalry reached Charleroi before ten o'clock in the morning, but an unfortunate and exasperating accident befallen a messenger left the infantry immediately behind without instructions. The cavalry were impotent to force the bridge crossing the river Sambre, which runs through the town, until the main body should appear, and it was not until past noon that the main body began crossing the Sambre by the Charleroi bridge. The Emperor had probably intended to fight immediately after having crossed the river. Gosselies, to the north, was strongly held; and had all his men been over the Sambre in the early afternoon as he had intended, an action fought suddenly, by surprise as it were, against the advance bodies of the First Prussian Corps, would have given the first example of that destruction of the enemy in detail which Napoleon intended. But the delays in the advance, rapid as it had been, now forbade any such good fortune. The end of the daylight was spent in pushing back the head of the First Prussian Corps (with a loss of somewhat over 1000 men), and when night fell upon that Thursday evening, the 15th of June, the French held Charleroi and all the crossings of the Sambre, but were not yet in a position to attack in force. Of the left, the First Corps were but just over the Sambre; on the right, that is, of the Fourth Corps, some units were still upon the other side of the river; while, of the centre, the _whole_ of the Sixth Corps, and a certain proportion of cavalry as well, had still to cross! Napoleon had failed to bring the enemy to action; that enemy had fallen back upon Fleurus, pretty nearly intact.[4] All the real work had evidently to be put off, not only until the morrow, but until a fairly late hour upon the morrow, for it would take some time to get all the French forces on to the Belgian side of the river. When this should have been accomplished, however, the task of the next day, the Friday, was clear. It was Napoleon's business to fall upon whatever Prussian force might be concentrated before him and upon his right and to destroy it, meanwhile holding back, by a force sent up the Brussels road to Quatre Bras, any attempt Wellington and his western army might make to join the Prussians and save them. That night the Duke of Wellington's army lay in its cantonments without concentration and without alarm, guessing nothing. The head of Wellington's First Corps, the young Prince of Orange, who commanded the Netherlanders, had left his headquarters to go and dine with the Duke in Brussels.