Less than three hours after the first attack the Messines-Wytschaete Ridge was stormed. The British pushed their advance along the entire sector south of Ypres, from Observation Ridge to Ploegsteert Wood to the north of Armentieres. Later in the day the German rear defenses, which ran across the base of the salient, were assaulted. Here the Germans had concentrated strong forces and the British encountered stiff opposition, but by nightfall the whole rear German position along a five-mile front to a depth of three miles was secure in British hands. The Canadians, who were in the forefront of all the fighting, had an enjoyable day of it, unsurpassed since they swept the Germans from Vimy Ridge. In the course of the day's fighting the British captured over 7,000 prisoners and a large number of guns of all calibers. The Germans, it was estimated, had about 30,000 casualties, and the British less than a third of that number. Eyewitnesses to this spectacular and dramatic operation have described the shattering effect the terrific explosions had on the Germans defending the positions, especially on those protecting the ill-famed Hill 60, where so many brave British soldiers had perished in previous fights. When this hill burst open and a dense mass of fiery clouds and smoking rocks shot skyward, the British troops assigned to take the position and while still some distance away were thrown down by the violence of the concussion. But no one was injured, and finding their footing they dashed on in the direction of the hill. Below Mount Sorrel and in Armagh Wood they encountered groups of Jaegers and Wuerttembergers, who crawled out of holes in the still quivering earth, and, shaking with terror, weakly raised their hands in token of surrender. There was no desire to fight left in these men, but where the dugouts had not been shattered by British fire and were partly intact hundreds crouched in the dark and could only be persuaded to come into the open when bombs were hurled among them. In other places the explosions had not produced such terrifying effects on the Germans, and the British met with stubborn resistance. This was the case in the neighborhood of the Chateau Matthieu, to the west of Hollebeke, which was strongly held and where the Londoners who engaged the Germans had a strenuous time of it before they gained the upper hand. The British had looked for stout resistance from the enemy in a street of fortresslike houses built of huge blocks of concrete six feet thick, but their shell fire had done its work so thoroughly that most of the structures were in ruins, while the occupants of those that remained intact were too cowed and panic-stricken to make any but the feeblest defense. For the first time on anything like a large scale the British leveled woodlands by spraying them with drums of burning oil, thus laying bare hidden trenches and gun emplacements and clearing the way for their infantry to advance.