Scarcely had the Prussian retreat begun in the darkness, when officers pressed up to Gneisenau, on whom now devolved all responsibility, for instructions as to the line of march.  At once he gave the order to push northwards to Tilly.  General Reiche thereupon pointed out that this village was not marked upon the smaller maps with which colonels were provided; whereupon the command was given to march towards the town of Wavre, farther distant on the same road.  An officer was posted at the junction of roads to prevent regiments straying towards Namur; but some had already gone too far on this side to be recalled—­a fact which was to confuse the French pursuers on the morrow.  The greater part of Thielmann’s corps had fallen back on Gembloux; but, with these exceptions, the mass of the Prussians made for Tilly, near which place they bivouacked.  Early on the next morning their rearguard drew off from Sombref; and, thanks to the inertness of their foes, the line of retreat remained unknown.  During the march to Wavre, their columns were cheered by the sight of the dauntless old Field-Marshal, who was able to sit a horse once more.  Thielmann’s corps did not leave Gembloux till 2 p.m., but reached Wavre in safety.  Meanwhile Buelow’s powerful corps was marching unmolested from the Roman road near Hannut to a position two miles east of Wavre, where it arrived at nightfall.  Equally fortunate was the reserve ammunition train, which, unnoticed by the French cavalry, wound northwards by cross-roads through Gembloux, and reached the army by 5 p.m.[496]

In his “Commentaries,” written at St. Helena, Napoleon sharply criticised the action of Gneisenau in retreating northwards to Wavre, because that town is farther distant from Wellington’s line of retreat than Sombref is from Quatre Bras, and is connected with it only by difficult cross-roads.  He even asserted that the Prussians ought to have made for Quatre Bras, a statement which presumes that Gneisenau could have rallied his army sufficiently after Ligny to file away on the Quatre Bras chaussee in front of Napoleon’s victorious legions.  But the Prussian army was virtually cut in half, and could not have reunited so as to attempt the perilous flank march across Napoleon’s front.  We shall, therefore, probably not be far wrong if we say of this criticism that the wish was father to the thought.  A march on Quatre Bras would have been a safe means of throwing away the Prussian army.[497]

To the present writer it seems probable that Gneisenau’s action, in the first instance, was undertaken as the readiest means of reuniting the Prussian wings.  But Gneisenau cannot have been blind to the advantages of a reunion with Wellington, which a northerly march would open out.  The report which he sent to his Sovereign from Wavre shows that by that time he believed the Prussian position to be “not disadvantageous”; while in a private letter written at noon on the 17th he expressly states that the Duke will accept battle at Waterloo if the Prussians help him with two army corps.  Gneisenau’s only doubts seem to have been whether Wellington would fight and whether his own ammunition would be to hand in time.  Until he was sure on these two points caution was certainly necessary.