If fighting went on only at ground level Bloch would win at this stage, but here it is that the aeroplane comes in. From the ground it would be practically impossible to locate the enemies' dug-outs, secondary defences, and batteries. But the aeroplane takes us immediately into a new grade of warfare, in which the location of the defender's secondary trenches, guns, and even machine-gun positions becomes a matter of extreme precision--provided only that the offensive has secured command of the air and can send his aeroplanes freely over the defender lines. Then the preliminary bombardment becomes of a much more extensive character; the defender's batteries are tackled by the overpowering fire of guns they are unable to locate and answer; the secondary dug-outs and strong places are plastered down, a barrage fire shuts off support from the doomed trenches, the men in these trenches are held down by a concentrated artillery fire and the attack goes up at last to hunt them out of the dug-outs and collect the survivors. Until the attack is comfortably established in the captured trench, the fire upon the old counter attack position goes on. This is the grade, Grade B2, to which modern warfare has attained upon the Somme front. The appearance of the Tank has only increased the offensive advantage. There at present warfare rests. There is, I believe, only one grade higher possible. The success of B2 depends upon the completeness of the aerial observation. The invention of an anti-aircraft gun which would be practically sure of hitting and bringing down an aeroplane at any height whatever up to 20,000 feet, would restore the defensive and establish what I should think must be the final grade of war, A3. But at present nothing of the sort exists and nothing of the sort is likely to exist for a very long time; at present hitting an aeroplane by any sort of gun at all is a rare and uncertain achievement. Such a gun is not impossible and therefore we must suppose such a gun will some day be constructed, but it will be of a novel type and character, unlike anything at present in existence. The grade of fighting that I was privileged to witness on the Somme, the grade at which a steady successful offensive is possible, is therefore, I conclude, the grade at which the present war will end. 2