During these redispositions, probably induced to do so by evidences patent to him that large troop movements were in progress, the enemy carried out a very heavy gas bombardment and maintained it for some hours over the whole of the front which was being taken over by the French.
The wind blowing from the south, the gas, which was unusually dense, drifted over the whole areas both of the Fourth Australian and the 32nd British Divisions, and caused a large number of gas casualties, which weakened the available garrisons of these sectors.
The Second and Fifth Divisions were brought up on the night of August 26th to relieve the First Division, which had worthily earned a rest, and by these redispositions my whole frontage, which, in spite of the reduction effected, still exceeded nine miles, was organized to be held by four Divisions, counting from south to north as follows: 32nd Division, Fifth Division, Second Division and Third Division, the latter lying north of the River Somme.
The First and Fourth Divisions were each sent back, the former to a pleasant reach of the Somme near Chipilly, and the latter to the neighbourhood of Amiens, there to have a long rest and to recuperate after their strenuous labours. These two Divisions were, I had resolved, to be kept in reserve for any tour de force, the need for which might arise later. This disposition was based on intuition rather than on reasoning; but the event proved that it was a fortunate decision; for, at a juncture, three weeks later, when a great opportunity presented itself, these two Divisions, then fully rested, proved of priceless value.
The Third Division held my front north of the Somme, and their presence there ensured my unchallenged tactical control of that important river valley. Numerous crossings had been systematically destroyed by the enemy, as he was being driven back from bend to bend, and as systematically repaired by my indefatigable engineer and pioneer services, as fast as the ground passed under our control.
Reconstruction of bridges and culverts is as tedious a business as their demolition is expeditious. A charge of gun-cotton, placed in the right spot, a primer, a short length of fuse, or an electric lead to a press button are all that are needed, and a single sapper standing by with a match, to be lighted at the last moment, can do all that is necessary to provide three days' work for a whole Company of Engineers.
Nevertheless, the control of the river valley was of inestimable advantage, for it enabled me to carry out a policy of continuous and rapid repair. Consequently, during the whole of our subsequent advance, every means of traversing the valley from south to north, which had been tampered with, was soon restored, as fast as my infantry had made good their advance beyond the ruined crossing.
This facility was to have an important bearing upon my freedom of action, not many days later, when the Corps came head on to the north and south stretch of the Somme, and found every bridge gone. That circumstance alone would have proved an irretrievable misfortune, if I had not had already available numerous restored crossings upon the east and west reach of the river. For by that means, my ability to pass troops and guns rapidly from one bank of the Somme to the other remained unimpaired.
Before leaving the line, the First Division had captured Cappy and advanced its line on the right to the western outskirts of Foucaucourt, while the Third Division had possessed itself of Suzanne. This was the situation when, on the night of August 26th, the Second and Fifth Divisions came into the line. Conferences with the four line Divisions were held both on the 25th and 26th August, in order to ensure co-ordinate action for the process of hustling the enemy across the Somme.
I was, at this stage, sorely perplexed by the uncertain attitude of the Fourth Army. I was all for pushing on energetically, and received General Rawlinson's approval to do so on August 24th; but on the very next day he enunciated a diametrically opposite policy, which greatly embarrassed me.