Where was Germany's hopes for a quick victory on the western front were ended?

Following the outbreak of World_War_Iin 1914, the German_Empirearmy opened the Western Front by first invading Luxembourgand Belgium, then gaining military control of important industrial regions in France. The tide of the advance was dramatically turned with the First_Battle_of_the_Marne. Both sides then dug in along a meandering line of fortified Trench_warfare, stretching from the North_Seato the Switzerlandfrontier with France. This line remained essentially unchanged for most of the war.