The third and most important cause lay in the cunning skill with which the German barrage was used. We have referred above to the manning of the German parapets by their garrisons after our barrage had passed over; but not in every case did this happen. In many instances a greater refinement of skill was exhibited. As the British barrage lifted off the first objective and the leading waves of the assault poured over it, down came the enemy barrage like a dense curtain, cutting them off for ever from their supports and their supplies. The barrage having thus trapped them, the front trench filled with Germans swarming up from their subterranean shelters, and these poured a hail of machine-gun fire into the backs of our waves which were pushing forward to the next line. After the experience of two more years of organised trench to trench attacks, it may be that failure for the reasons detailed above seems a little obvious; but it would not be fair to pass them over without pointing out that this was the first trench to trench attack of the whole War which had been organised on so vast a scale, and it was clearly impossible to provide against all eventualities when there was no previous experience to act as a guide. It should be remembered that in the south, where a greater degree of surprise was attained, the arrangements for attack--which were substantially the same as in the north--worked splendidly and resulted in marked success. And in subsequent attacks attention was paid to the experience gained on this great opening day of the First Somme Battle in increasing the strength of counter-battery artillery and in making more efficient arrangements for "mopping-up" captured lines. As regards the 168th Brigade attack, in addition to the above general criticisms, it may be remarked that the event showed that on the left of the Brigade at least there was insufficient weight in the attack. The Scottish on the right had to advance 250 yards and were able to carry their objectives; but on the left the depth to be penetrated was about 450 yards, and this proved too great for the available strength of the Rangers, who were organised in five waves, even when strengthened by two additional waves supplied by the companies of the 1/4th Londons. A deal of congestion in the trenches and a great many casualties were caused by the lack of those deep dugouts with which the Germans were so well supplied, and in the case of the 1/4th Londons at any rate it seems likely that they might have been of more use when called upon had they been able to obtain efficient shelter during the hours of waiting.