German prisoners captured around Lens spoke of the awful havoc wrought by the British gas cylinders and gas shells. The German First Guards Reserve Regiment lost twenty men when a gas shell exploded in the cellar where they lay asleep. Another company of this regiment had seventeen casualties from the same cause in one day. The failure of Germany to get a sufficient supply of rubber was a contributing cause of the gas fatalities. German masks were of poor quality and tore easily. Masks of soft leather were used by them at this time on some parts of the Lens front. The objection to masks of leather was that they could not be put on as easily as those made of rubber, a serious defect when a moment's delay might prove fatal.
Northumberland troops operating in the neighborhood of Villaret extended their gains southward 400 yards in an attack made on German trenches in the morning of September 11, 1917. During the day the Germans attempted three counterattacks with bombs on the new British positions but were driven off.
The French continued active in the Verdun region, where they had to defend themselves from frequent counterattacks. In the Champagne territory French troops struck a shrewd blow on September 11, 1917, when in successful raids they drove across the German trenches between St. Hilaire and St. Souplet and penetrated the second line. Here there was intense and deadly fighting. The German defenders were either killed or made prisoners, and the French captured large quantities of supplies.
North of Caurières Wood, northeast of Verdun, the French advanced line on a front of about 500 yards penetrated the German trenches and close fighting developed. This was the scene of continuous attacks and counterattacks for two days in which each side gained in turn a temporary ascendancy, but the result was indecisive. It was not until the night of September 14-15, 1917, that the French succeeded in ejecting the Germans from the greater part of the trench system here and took possession. In Champagne on September 14, 1917, a surprise attack made by the French in the region of Mont Haut was successfully carried out. A German observatory and a number of shelters and dugouts were destroyed and much damage wrought to the enemy defenses.
No important operation was attempted by the British troops around Lens for several days following, but bombardments were incessant. The Canadians, though constantly under fire and subjected day and night to strong attacks, firmly held their positions. The situation of the Germans in the center of Lens with an active enemy occupying high ground to the north and south was not a comfortable one. When they did fight it was with rage and despair. Prisoners taken told of the deadly effects of the British gas projectiles which wrought awful havoc among the troops herded in tunnels and dugouts. The constant bombardment of Lens had reduced the city to the same ruined condition as the suburbs. The subterranean caverns which the Germans had built by the forced labor of civilians two years and more before became death traps. Often they collapsed under a heavy bombardment, burying alive whole companies in the ruins. Again, as frequently happened, a shell would explode inside the caves with fatal results to the occupants.
The Germans had every reason to wish that they had never introduced poison gas in warfare, for as employed by the British it had become a far deadlier destructive weapon than in their own hands. Many times during these days the Canadians had flooded the city with gas which soaked down into the tunnels and dugouts and stifled men in their sleep, or they died with their masks on if they delayed a second too long.
After days of raids and counterattacks insignificant when considered as separate operations, but important in the aggregate, British troops under Field Marshal Haig delivered a powerful attack against the German lines east of Ypres on an eight-mile front on September 20, 1917. According to an eyewitness, the barrage that preceded the advance was the heaviest on record.
The British were successful in attaining all their objectives. The German center along the Ypres-Menin road was penetrated to the depth of a mile.
Rain had fallen steadily during the night preceding the assault, but the assembling of the regiments assigned to the operation was carried through without a mishap. North Country troops carried the Inverness Copse. Australian troops stormed Glencorse Wood and Nonneboschen (Nun's Wood); Scottish and South African brigades captured Potsdam, Vampire, and Borey Farms; West Lancashire Territorials carried Iberian Farm and the strong point known as Gallipoli. After making a swift "clean-up" of these places and positions the British forces advanced on the final objectives.
Troops from the counties who drove forward on the right encountered fierce opposition in the woods north of the Ypres-Commines Canal, and in the vicinity of the Tower Hamlets, but cut through with mighty thrusts and gained the desired goal with light casualties. In the center North Country and Australian battalions pierced German positions to a depth of over a mile and won all their objectives, which included the village of Veldhoek and the western part of Polygon Wood. Zevenkote, farther north, was won and the London and Highland Territorials made a clean sweep of the second line of farms, including Rose, Quebec, and Wurst Farms, all on the line of their final objectives.