Pressing danger could only exist if Blucher had gone northwards, and northwards, therefore, in the Dyle valley, he should have diligently sought for traces of the Prussian retreat.'
Had Blucher gone eastwards, Grouchy, holding the Dyle, could easily have held back any future Prussian advance towards Wellington.
By nightfall the situation was all in favour of the allies; for Grouchy was now actually outside the four Prussian corps, who were by this time concentrated astride the Dyle at Wavre.
The marshal wrongly determined Groachy' on the 18th to continue his march to Wavre in a single column, and he determined, still more wrongly, to move by the right bank of the Dyle.
Grouchy was now urged by his generals, especially by Gerard, to march to the sound of the firing, but he refused to take their advice, and pushed on to Wavre, where he found the Prussians (Thielemann's corps of 16,00o men) holding the passages across the Dyle.