On both sides the concentration of artillery was very great. Though the bad weather had shackled our advance from the start, our staff yet hoped to gain the ridge of Passchendaele before winter set in. The Germans, too, held that the stake was high. Our guns, which were advanced as far as Wieltje and St. Jean and stood exposed in the open, became the object of persistent German shelling. Sound-ranging and aerial photography had reached a high development, and few of our batteries went undiscovered. For the Artillery life became as hard as for the Infantry. Gunner casualties were very numerous. Our batteries for hours on end were drenched in mustard-gas. Into Ypres as well large quantities of 'Yellow Cross' shells, cleverly mixed up with high-explosive, were fired with nocturnal frequency. The long range of the enemy's field-guns made the effect of these subtle gas-shells, whose flight and explosion were almost noiseless amid the din of our own artillery, especially widespread. The enemy's activity against our back area was at its height at the end of August, 1917. Casualty Clearing Stations were both bombed and shelled. Near Poperinghe nurses were killed. No service forward of Corps Headquarters but had its casualties. Our lorry-drivers' work was fraught with danger. The Germans were waging a war to the knife and employing every means to serve their obstinate resistance. [Illustration: VLAMERTINGE--THE ROAD TO YPRES] The 'defence in depth,' practised to some extent at Arras, had become the enemy's reply to our destruction by artillery of the trench systems on which, earlier in the war, he had relied with confidence. Destruction of prepared positions had reached so absolute a stage that the old arguments of wire and machine-guns brought up from deep dug-outs to fire over parapets, were no longer present. The ground to a distance of several thousand yards behind the enemy's front line could be, and had been, churned and rechurned into one brown expanse. For four miles east of Ypres there was no green space and hardly a yard of ground without its shell-hole. Positions where the enemy held out consisted in groups of concrete 'pill-boxes,' which had been made from Belgian gravel and cement in partial anticipation of this result of the artillery war. They in all cases were carefully sited and so small (being designed to hold machine-guns and their teams) that their destruction by our heavy shells was almost impossible. These 'pill-boxes' were also so designed as to support each other, that is to say, if one of them were captured, the fire of others on its flanks often compelled the captors to yield it up. Garrisons were provided from the _elite_ of the German army. One cannot but admire the steadfastness with which, during this phase of warfare, these solitary strongholds held out. Indeed, the only way to cope with this defence was to press an advance on a wide front to such a depth as to reduce