its succour rendered probable. But though Marlborough had
established his headquarters before the place by the evening of the 27th
of June, and Eugene upon the next day, the 28th, though trenches were
opened in the first week of July and the first of the heavy fighting
began upon the 8th of that month, though the town itself was occupied
after a fortnight's struggle, yet it was not until the 3rd of September
that the citadel surrendered.

This protracted resistance largely determined what was to follow. While it
lasted no action could be undertaken against Villars. Meanwhile the French
forces were growing stronger, and, most important of all, the first
results of the harvest began to be felt.

Tournai once taken, it was the business of the allies to pierce the French
line of defence as soon as possible, and with that object to bring Villars
to battle and to defeat him.

The plan chosen for this object was as follows:--

The allied army to march to the extreme right of the positions which the
French could hope to defend. There the allies would contain the little
garrison of Mons. Thither the mass of the French forces must march in
order to bar the enemy's advance upon Paris, and upon some point near Mons
the whole weight of the allies could fall upon them, destroy them, and
leave the way to the capital open.

[Illustration: Sketch Map showing how the Lines of La Bassee blocked the
advance of the Allies on Paris, and Marlborough's plan for turning them by
the successive capture of Tournai and Mons.]

The plan was strategically wise. The lines of La Bassee proper could not
be pierced, but this right extremity of the French positions was backed by
easy country; the swamps, canals, and entrenchments of the main line to
the north and west were absent. With the defeat of the inferior French
forces at this point all obstacle to an advance into the heart of France
would be removed.

The plan was as rapidly executed as it was skilfully devised. Actually
before the capitulation of the citadel of Tournai, but when it was
perceived that that capitulation could only be a matter of hours, Lord
Orkney had begun to advance upon the neighbourhood of Mons. Upon the day
of the capitulation of Tournai, the Prince of Hesse-Cassel had started for
Mons, Cadogan following him with the cavalry. Less than twenty-four hours
after Tournai had yielded, the whole allied army was on the march
throughout the night. Never was a military oper