By February 15, 1916, the British first-line trenches on a 600 to 800 yards' front fell to the Germans in assaults on the Ypres salient, carried by a bayonet charge after artillery preparation. Most of the defenders were killed and forty prisoners taken. The assaults extended over a front of more than two miles. The trench now captured by the Germans had frequently changed hands during the past twelve months, and for that reason was facetiously called "the international trench." The brunt of the fighting here fell upon the Canadians, who were withdrawn from the trench owing to the furious bombardment, and sheltered in the second-line trench. The German infantry consequently met with no opposition at the former, but when they approached the latter the Canadians opened a murderous fire with rifles and machine guns, dropping their enemies in hundreds. A few, however, managed to reach the trenches, when the Canadians sprang out and charged with bayonets, rushed the Germans back to and across the first-line trenches again, which were then reoccupied. It was the Canadian First Division that had blocked the German path to Calais in the spring of 1915 almost at the same point. Activity on the west front on the 18th was largely confined to the Ypres district. British troops attempted to recapture their positions to the south of Ypres, simultaneously bombarding the German trenches to the north of the Comines Canal. By February 20, 1916, as a result of the continuous fighting north of Ypres, the British had lost on the Yser Canal what the German official report described as a position 350 meters long, and the British statement as "an unimportant advanced post." The Germans took some prisoners and repelled several day and night attacks by the British to recover the ground. In Champagne, uninterrupted artillery actions continued apparently without much advantage to either side. The German works north of Souain were particularly visited. On February 5, 1916, the French bombarded the German works on the plateau of Navarin, wrecking trenches and blowing up several munition depots. Some reservoirs of suffocating gas were also demolished, releasing the poisonous fumes, which the wind blew back across the German lines. On the 13th the French were able to report a further success northeast of the Butte du Mesnil, where they took some 300 yards of German trenches. A counterattack by night was also repulsed, the Germans losing sixty-five prisoners. They succeeded, though, in penetrating a small salient of the French line between the road from Navarin and that of the St. Souplet. They also captured, on the 12th, some sections of advanced trenches between Tahure and Somme-Py, gaining more than 700 yards of front.