The conditions which I had sought in my previous negotiations with the Army Commander were, I found, conceded to me almost to the full extent. My battle front was to be reduced from eleven miles to a little over 7,000 yards. It would, in fact, extend from the Somme, as the northern, to the main Péronne railway, as the southern flank. And—what was equally important, and profoundly welcome—the First Australian Division was shortly to be relieved in Flanders, and would at last join my Corps, thus for the first time in the war bringing all Australian field units in France under one command.

The Canadians were to operate on my right, and further south again the First French Army (Debenay) was to supply a Corps to form a defensive flank for the Canadians. The Third British Corps was to carry out for me a similar function on my northern flank. Thus, four Corps in line were to operate, the two central Corps carrying out the main advance, while the two outer flank Corps would be employed further to broaden the base of the great salient which the operation would create.

The Cavalry Corps would appear in the battle area also, with all preparations made for a rapid exploitation of any success achieved. The utility of the Cavalry in modern war, at any rate in a European theatre, has been the subject of endless controversy. It is one into which I do not propose to enter. There is no doubt that, given suitable ground and an absence of wire entanglements, Cavalry can move rapidly, and undertake important turning or enveloping movements. Yet it has been argued that the rarity of such suitable conditions negatives any justification for superimposing so unwieldy a burden as a large body of Cavalry—on the bare chance that it might be useful—upon already overpopulated areas, billets, watering places and roads.

I may, however, anticipate the event by saying that the First Cavalry Brigade was duly allotted to me, and did its best to prove its utility; but I am bound to say that the results achieved, in what proved to be very unsuitable country beyond the range of the Infantry advance, did not justify the effort expended either by this gallant Brigade or by the other arms and services upon whom the very presence of the Cavalry proved an added burden.

For the full understanding of subsequent developments both during and after the battle it becomes of special importance to consider the proposed rôle of the Third Corps in relation to my left flank. It is to be remembered that the Fourth Army decided that the River Somme was to be the tactical boundary between the two Northern Corps. It was not competent for me to criticize this decision at the time, but I am free now to say that I believed such a boundary to have been unsuitable, and the event speedily proved that it was.

It is always, in my opinion, undesirable to select any bold natural or artificial feature—such as a river, ravine, ridge, road or railway—as a boundary. It creates, at once, a divided responsibility, and necessitates between two independent commanders, and at a critical point, a degree of effective co-operation which can rarely be hoped for. It is much better boldly to place a unit, however large or small, astride of such a feature, so that both sides of it may come under the control of one and the same Commander.

This was especially the case in this part of the Somme Valley which is broad, and has an ill-defined central line, tortuous, and with the slopes on either side tactically interdependent; but most of all because, as I have already described, the high plateau on the north completely overlooks the relatively lower flats on the south of the river. The point I am trying to make should be borne in mind, for I believe it has been fully borne out by subsequent events.

The decision standing, however, as it did, it fell to the task of the Third Corps to make an assault (concurrently with that of the Australian Corps south of the river) for the capture of the whole of that reach of the river known as the Chipilly Bend, and of all the high ground on the spur which that bend enfolds. The object was to deprive the enemy of all ground from which he could look down upon my advancing left flank, or from which he could bring rifle or artillery fire to bear upon it.