press themselves upon us as we consider the total result of
that critical day, the 16th of June, which saw Ney fail to hold the
Brussels road at Quatre Bras, and there to push away from the advance on
Brussels Wellington's opposing force, and which also saw the successful
escape of the Prussians from Ligny, an escape which was to permit them to
join Wellington forty-eight hours later and to decide Waterloo.

The first is the capital importance, disastrous to the French fortunes, of
Erlon's having been kept out of both fights by his useless march and
countermarch.

[Illustration: THE ELEMENTS OF QUATRE BRAS.]

The second is the extraordinary way in which Wellington's command came up
haphazard, dribbling in by units all day long, and how that command owed
to Ney's caution and tardiness, much more than to its own General's
arrangements, the superiority in numbers which it began to enjoy from an
early phase in the battle.

I will deal with these two points in their order.

* * * * *

As to the first:--

The whole of the four days of 1815, and the issue of Waterloo itself,
turned upon Erlon's disastrous counter-marching between Quatre Bras and
Ligny upon this Friday, the 16th of June, which was the decisive day of
the war.

What actually _happened_ has been sufficiently described. The useless
advance of Erlon's corps d'armee towards Napoleon and the right--useless
because it was not completed; the useless turning back of that corps
d'armee towards Ney and the left--useless because it could not reach Ney
in time,--these were the determining factors of that critical moment in
the campaign.

In other words, Erlon's zigzag kept the 20,000 of the First Corps out of
action all day. Had they been with Ney, the Allies under Wellington at
Quatre Bras would have suffered a disaster. Had they been with Napoleon,
the Prussians at Ligny would have been destroyed. As it was, the First
Army Corps managed to appear on _neither_ field. Wellington more than held
his own; the Prussians at Ligny escaped, to fight two days later at
Waterloo.

Such are the facts, and they explain all that followed (see Map, next
page).

But it has rightly proved of considerable interest to historians to
attempt to discover the human motives and the personal accidents of
temperament and misunderstanding which led to so extraordinary a blunder
as the utter waste of a whole army corps during a whole day, within an
ar