fect its junction with the eastern half at Quatre Bras
(Q), a few miles off from Ligny (P). The situation on the night of Friday,
June 16th, at the end of this second step, is that represented in this
second sketch map.

[Illustration]

Believing the Prussians (D E F) to be retreating from Ligny towards their
base eastward, and not northwards, Napoleon more or less neglects them and
concentrates his main body in order to follow up Wellington's western half
(A B C), and in the hope of defeating _that_ in its turn, as he has
already defeated the eastern or Prussian half (D E F) at Ligny (P). With
this object Napoleon advances northward during all the third day,
Saturday, June 17th. Wellington (A B C) retreats north before him during
that same day, and then, on the morrow, the 18th, Sunday, turns to give
battle at Waterloo (W). Napoleon engages him with fair chances of success,
and the situation as the battle begins at midday on the 18th is that
sketched in this third map.

[Illustration]

But unexpectedly, and against what Napoleon had imagined possible, the
Prussians (D E F), when defeated at Ligny (P), did not retreat upon their
base, and have not so suffered from their defeat as to be incapable of
further action. They have marched northward parallel to the retreat of
Wellington; and while Napoleon (X Y Z) is at the hottest of his struggle
with Wellington (A B C) at Waterloo (W), this eastern or Prussian half (D
E F) comes down upon his flank at (R) in the middle of the afternoon, and
by the combined numbers and disposition of this double attack Napoleon's
army is crushed before darkness sets in.

[Illustration]

Such, in its briefest graphic elements, is the story of the four days.

It will be observed from what we have said that the whole thing turns upon
the incompleteness of Napoleon's success at Ligny, and the power of
_retreating northward_ left to the Prussians after that defeat.

When we come to study the details of the story, we shall see that this,
the Prussian defeat at Ligny, was thus incomplete because one of
Napoleon's subordinates, Erlon, with the First French Army Corps, received
contradictory orders and did not come up as he should have done to turn
the battle of Ligny into a decisive victory for Napoleon. A part of
Napoleon's forces being thus neutralised and held useless during the fight
at Ligny, the Prussian army escaped, still formed as a fighting force, and
still capable of re