At first he thought of marching against Blucher’s rear, but very little reflection showed him that Thielemann would in the meantime attack _his_ rear, and his 30,000 men would be caught between two forces. Then Vandamme, always impetuous and for action, proposed that they should march straight on Brussels, set free the French prisoners there, and retire by Enghien and Ath to Lille. This was a daring but futile plan. Of what use would such a movement have been, even had it been successfully carried out? To march boldly completely round the rear of the allied armies, liberate a few prisoners, and then march off in the opposite direction, would have been to waste the only formed body left of all Napoleon’s army. And what would Thielemann do in the meantime? There was now no hope of winning over Brussels or the Dutch-Belgians, otherwise there would have been some weight in Vandamme’s extraordinary proposal. But Grouchy counselled otherwise. He knew that he already ran the risk of being attacked in flank, most probably in rear, by a portion of Blucher’s army, while Thielemann would certainly advance again as soon as the retreat began. He therefore decided to retreat on Namur, where he would act further according to circumstances. It was useless as well as dangerous to direct his retreat towards the line taken by the remnants of Napoleon’s host, where all would be confusion; it was better by far to retreat on his own line and endeavour to preserve his troops intact as long as possible. At Namur, he might do great things yet; for Namur had not, like Charleroi, witnessed first the triumph and then the downfall of Napoleon’s last plans. Even at this moment, Grouchy was already in danger of being attacked in rear. For Pirch I. had received orders on the night of the 18th to march towards Namur with his Corps (the Second) and cut off Grouchy from the Sambre; and by the time that Grouchy heard of the rout, he had reached Mellery, on the Tilly-Mont St Guibert road, and 8 miles in Grouchy’s rear. But his troops were exhausted, and his Divisions scattered--the Sixth, Seventh, Eighth Divisions, twenty-four squadrons of his reserve cavalry, and the reserve artillery, were with him; but the Fifth Division and the rest of his cavalry were pursuing the French on the Charleroi road. So Pirch ordered a halt at Mellery.