The Marne is a strategic river in France that played an important role in World War I. It was the site of two major battles in 1914 and 1918, both of which were decisive victories for the Allies. The first battle, known as the First Battle of the Marne, was fought between the French and German armies and resulted in a French victory. The second battle, known as the Second Battle of the Marne, was fought between the Allies and the Germans and resulted in an Allied victory. The Marne is a major tributary of the Seine River and is located in northeastern France.