The First Battle of Ypres (First Ypres) took place between the 19th of October and the 22nd of November 1914. French, British and Belgian troops took their positions around Ypres to defend a well-defined salient. The Germans began an offensive to break through the allied line and to capture the ports of Dunkirk, Calais, and Boulogne. Before the attack against Ypres, the Belgian defences on the Yser River (Battle of the Yser) had already stopped the German advance. The fighting around Ypres lasted until 22 November, when winter forced a break in hostilities. Both armies suffered many casualties. From 1914 onwards, the Germans began to dig trenches on high ground, particularly the low ridges that surround Ypres to defend themselves from fire by the allied forces. When the Allies realised that a breakthrough was impossible, they also started to dig themselves in. They were at a disadvantage, however, because they had to use the topographically lower areas, closer to the city and beneath the surrounding ridges. After only a few months German and Allied trenches were dug all along the Western Front, from the North Sea Canal to the Swiss border.