Moselle valley in the context of "Alsace–Lorraine"

Alsace–Lorraine (German: Elsaß–Lothringen), officially the Imperial Territory of Alsace–Lorraine (German: Reichsland Elsaß–Lothringen), was a territory of the German Empire which is now part of France. It was established in 1871 by the German Empire after it had occupied the region during the Franco-Prussian War. The region was officially ceded to the German Empire in the Treaty of Frankfurt. French resentment about the loss of the territory was one of the contributing factors to World War I. Alsace–Lorraine was annexed in practice by France at the war's end following Germany's defeat in 1918, but only formally ceded back in 1920 as part of the Treaty of Versailles.

Geographically, Alsace–Lorraine encompassed most of Alsace and the Moselle department of Lorraine; the Alsatian part lay in the Rhine Valley on the west bank of the Rhine River, east of the Vosges Mountains, while the section initially in Lorraine was in the upper Moselle valley to the north of the Vosges. Politically, it was the only subdivision of the German Empire considered an "Imperial Territory"; as such, it was under the direct administration of the Imperial German state, rather than a quasi-sovereign constituent of the federal Empire. It was granted a legislature and limited internal autonomy in 1911.