llington's command on the morning of the 16th when he was writing his
letter to Blucher and the positions which Wellington, in that letter,
erroneously ascribes to them. It will show the reader the wide difference
there was between Wellington's idea of where his troops were and their
actual position on that morning. It needs no comment. It is sufficient in
itself to explain why the action at Quatre Bras consisted not in a set
army meeting and repelling the French (it could have destroyed them as
things turned out, seeing Erlon's absence), but in the perpetual arrival
of separate and hurried units, which went on from midday almost until
nightfall.

IV

THE ALLIED RETREAT AND FRENCH ADVANCE UPON WATERLOO AND WAVRE

When the Prussians had concentrated to meet Napoleon at Ligny they had
managed to collect, in time for the battle, three out of their four army
corps.

These three army corps were the First, the Second, and the Third, and, as
we have just seen, they were defeated.

But, as we have also seen, they were not thoroughly defeated. They were
not disorganised, still less were the bulk of them captured and disarmed.
Most important of all, they were free to retreat by any road that did not
bring them against their victorious enemy. In other words, they were free
to retreat to the north as well as to the east.

The full importance of this choice will, after the constant reiteration of
it in the preceding pages, be clear to the reader. A retreat towards the
east, and upon the line of communications which fed the Prussian army,
would have had these two effects: First, it would have involved in the
retirement that fresh Fourth Army Corps under Bulow which had not yet come
into action, and which numbered no less than 32,000 men. For it lay to the
east of the battlefield. In other words, that army corps would have been
wasted, and the whole of the Prussian forces would have been forced out of
the remainder of the campaign. Secondly, it would have finally separated
Blucher and his Prussians from Wellington's command. The Duke, with his
western half of the allied forces, would have had to stand up alone to the
mass of Napoleon's army, which would, after the defeat of the Prussians at
Ligny, naturally turn to the task of defeating the English General.

Now the fact of capital importance upon which the reader must concentrate
if he is to grasp the issue of the campaign is the fact that the French
staff fell into an