World Wars I and II were fought against the Germans on the western front. Whereas the Western Front in the First World War was very static (only moving a few miles each way during the course of the whole war, the western front in the Second World War lasted less than a year with the crushing defeat of France

Western Front - World War I - happened on 1914-08-04.

Eastern Front - World War II - happened on 1941-06-22.

Are you referring to World War I or World War II?

In World War I, Germany was the reason for the opening of the Western Front, by the invasion of Belgium in order to attack France.

In World War II, Germany, again, was the reason for the opening of the Western Front. First, they attacked Denmark and Norway (which would be more considered a Northern Front) which was the first contact of German and Allied troops (the British deployed into Norway, but retreated). The Germans then attacked the Benelux countries and France, all falling in a matter of weeks.

In both world wars, the initial front was the Eastern Front (on a German standpoint).

The Western front