Meanwhile, a new German offensive was being prepared, which their High Command believed would prove irresistible, thanks to the use of a new weapon, as murderous as it was unexpected. Although Germany had signed the clause of the Hague Convention (July 29, 1899), which prohibits the use of =asphyxiating gas=, the unscrupulous leaders now made use for the first time of this treacherous weapon. In accordance with their usual practice, they claimed that the British used the gas first, and that they used it only in reprisal. Needless to say, this assertion was pure fiction. On April 22 the front ran as follows: Belgian troops held the canal; the French 45th Colonial Infantry Division, resting on the canal, and passing through Bixschoote, linked up with the troops of the Canadian 3rd Brigade. Throughout the morning of April 22, the Germans bombarded the first lines, while the roads behind were swept by the fire of the heavy artillery, including 16½-in. guns. The bombardment continued into the afternoon. Suddenly, at about 4 p.m., there rose from the German trenches, opposite the lines occupied by the French Colonial troops, a strange opaque cloud of greenish-yellow fumes. A light breeze from the north-east wafted this cloud towards the French, who, a few moments later, fell gasping for breath in terrible agony. Terror spread through the ranks, especially among the African troops. A panic inevitably followed, which quickly spread from the front to the rear lines. Behind that cloud of gas the German troops advanced, protected by a heavy barrage and intense machine-gun fire. The French Colonial troops fell back several miles towards Ypres, and the Germans took Steenstraat, Het Sas and Pilkem, together with many prisoners. The withdrawal of the French uncovered the left flank of the Canadians, who were on their right, and they in turn were obliged to fall back, leaving four guns in the hands of the Germans. In the afternoon the Canadians, rallying, took the offensive, recovered part of the lost ground between Steenstraat and Langemarck, together with their guns, and inflicted a sanguinary defeat on the Germans. [Illustration: THE FIRST GERMAN POISON-GAS ATTACK _(April 24, 1915.)_] Further north, on the Yser Canal, the enemy took advantage of the disorder caused by the gas to cross at Steenstraat Bridge, and reached the village of Lizerne near Zuydschoote, where they strongly entrenched themselves. But Zouaves, aided by Belgians, counter-attacked in force, retook Lizerne, and advanced along the canal. The greatest German effort was made on April 25 against the British lines. The attacking troops had been grouped on both sides of the railway from Ypres to Roulers, near Broodseinde, but in spite of fierce attacks they could not break the British lines, and once more their dastardly methods failed them.