​MOSELLE-LINE, the designation of a line of French barrier forts (forts d'arrêt) on the upper Moselle between the fortresses ​of Épinal and Belfort (see these articles, also Meuse Line and articles referred to therein). The purpose of this line, the separate forts of which command the relatively few lines of advance from upper Alsace through the Vosges, is to deflect a possible German invasion from Alsace either towards Belfort or towards the open gap between Épinal and Toul called the Trouée d'Épinal.