Territorials and British and Canadian troops along the Yser on 22 April (see Map, p. 288). The attack had clearly been planned beforehand, because the preparation of the chlorine gas, arrangement of the gas-tubes along the front, and delay for the requisite conditions wind and weather required time; and the absence of any great concentration of troops merely showed that, in view of their commitments in the East, the Germans only sought at Ypres a local and tactical success. It was a mere accident that the gas attack north-east of the city followed upon strenuous fighting for Hill 60 at the south-east re-entrant, and the choice of locality was due to the German knowledge of the facts that the French regulars had been removed from the Yser and our own heavy guns from Ypres in order to take part in offensives farther south. The attack on Hill 60 was begun by us on 17th April, and its object was to acquire a gun position which commanded the German trenches in the Hollebeke district. The struggle lasted for five days and was one of the fiercest local combats in the war; at the end of it we were still on what was left of a mound of earth. The German offensive on the north-eastern front of Ypres was heralded by a bombardment of the city on the 20th which was designed as a barrage to cut off communications with the front along the roads which all ran through Ypres. On the evening of the 22nd the gas attack developed, and as the clouds of green vapour moved down on the French Territorials, unprovided with any sort of gas-masks and unprepared for the terrifying effects of poison en masse, they broke and fled, exposing the flank of the Canadians on their right from Langemarck to Grafenstafel. Never did troops make a more heroic debut in war under more trying conditions. Less affected by the gas than the French Territorials, the Canadians counter-attacked the German left flank, temporarily recaptured guns, and stayed the advance. The gaping breach on their left was partially filled by reinforcements from the 28th Division on the 23rd, but the Germans were across the canal at Het Sas and Lizerne, and the Canadians between St. Julien and Grafenstafel were fighting on three fronts. A second gas attack followed on the 24th, and presently St. Julien had to be abandoned. Reinforcements were, however, coming up; French regulars brilliantly recaptured Lizerne and Het Sas and secured the west bank of the canal against a German advance; and by the 29th the Canadians, who had saved the situation but had suffered heavily in the effort, were replaced by British troops. There was still desperate fighting to do for many days, and the curve of the Ypres salient had been reduced to a narrow oblong stretching from Ypres to Grafenstafel and the Polygon Wood, and little more than half in breadth what it was in length. A shortening of the line was inevitable, and it was effected with great skill and little loss on 3-4 May. But heavy bombardment continued to take a