212 The Great War fight still undecided. If the French version were correct and the advance is pressed, the Germans east of the Woevre must soon retreat to escape an enveloping movement, but the retreat had not yet come. What is vital to note in the Verdun operation is that the Germans were making a second terrific ef- fort to open a short road from German territory to French and free themselves from the intolerable burden of garrisoning Belgium, when every avail- able man was needed in France and on the eastern frontiers. If they succeeded they could retire the three army corps in Belgium, leaving containing forces between the fortresses of Maubeuge, Namur and Liege now in their hands, stationed behind the Meuse and the Sambre to protect their flank. If they failed, then a general retirement from the Aisne would again free Verdun from danger and the Ger- mans would still have to rely upon Belgian railways until another invasion of France permitted a third attempt on the Verdun-Toul barrier.