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