The French Counter-Offensive 87 German advance. Strassburg bore the same relation to the French. Antwerp in Belgium, Metz in Ger- man Lorraine, were both on the flank of invading forces. Consider now the possible effect of the French ad- vance. Its left had already passed the line of the Metz-Strassburg railway and was approaching Sa- verne; further advance would presently bring it into Lower Alsace, below Strassburg and on the Rhine. Meantime, its right was coming up from Belfort, by Muelhauscn, driving the German defence north to- ward Strassburg and east across the Rhine near Basel. Its centre was descending the valleys east of the sev- eral Vosges passes from the mountain of Donon to that of Barenkopf — one level with Strassburg, the other north of the French fortified post of Belfort. The effect of this advance if it could be success- fully pressed home would be to drive the Germans out of LIpper Alsace, surround Strassburg, and bring the French eastern frontier to the Rhine again. When forces had been detached to cover Strassburg and Neu Breisach, the main French Army would be free to advance down the Rhine toward Maycnce, where the Kaiser then was, or to cross the Rhine and drive north to Frankfort or east to Baden and South- ern Germany. In other words, just as the Germans had under- taken to sweep into Northern France, avoiding the great barrier forts from Epinal to Verdun, so the French were aiming at a counter-offeni>ive which