een no need to incur the heavy
casualties to be expected in an attempt to rush them. The time was now
approaching, although it had not yet arrived, when their capture would
become necessary; but from the positions we had now reached and those
which we expected shortly to obtain, I had no doubt that they could be
rushed when required without undue loss. An important part of the
remaining positions required for my assault on them was now won by a
highly successful enterprise carried out on the evening of September 14,
1916, by which the Wonderwork was stormed.

[Sidenote: Plan of combined attack.]

[Sidenote: Main effort against Rancourt and Fregicourt.]

The general plan of the combined allied attack which was opened on
September 15 was to pivot on the high ground south of the Ancre and
north of the Albert-Bapaume road, while the Fourth Army devoted its
whole effort to the rearmost of the enemy's original systems of defense
between Morval and Le Sars. Should our success in this direction warrant
it I made arrangements to enable me to extend the left of the attack to
embrace the villages of Martinpuich and Courcelette. As soon as our
advance on this front had reached the Morval line, the time would have
arrived to bring forward my left across the Thiepval Ridge. Meanwhile on
my right our allies arranged to continue the line of advance in close
co-operation with me from the Somme to the slopes above Combles, but
directing their main effort northward against the villages of Rancourt
and Fregicourt, so as to complete the isolation of Combles and open the
way for their attack upon Sailly-Saillisel.

A methodical bombardment was commenced at 6 a.m. on September 12, 1916,
and was continued steadily and uninterruptedly till the moment of
attack.

[Sidenote: Bombardment and infantry assault.]

At 6.20 a.m. on September 15, 1916 the infantry assault commenced, and
at the same moment the bombardment became intense. Our new heavily
armored cars, known as "tanks," now brought into action for the first
time, successfully co-operated with the infantry, and, coming as a
surprise to the enemy rank and file, gave valuable help in breaking down
their resistance.

[Sidenote: Tanks enter Flers.]

[Sidenote: High Wood carried.]

[Sidenote: Capture of the Quadrilateral.]

The advance met with immediate success on almost the whole of the front
attacked. At 8.40 a.m. "tanks" were seen to be entering Flers, followed
by large numbers