Its loss was not redeemed by the French offensive in Alsace and Lorraine. On 7 August a weak French force advanced through the Belfort gap and, finding still weaker forces to oppose it, proceeded to occupy Altkirch and Mulhouse, while a proclamation by General Joffre announced the approaching liberation of the provinces torn from France in 1870. It was a feeble and ill-conceived effort to snatch a political advantage out of a forbidding military situation. German reinforcements swept up from Colmar and Neu Breisach, and on the both the French were back within a few miles of the frontier, leaving their sympathizers to the vengeance of their enemies. More legitimate though not more successful was the French thrust in Lorraine. It had other motives than the political: it would, if pushed home, menace the left of the German armies in Belgium and disturb their communications; and a smaller success would avert the danger of a German advance in Lorraine which would threaten the right of the French on the Meuse. Accordingly, Generals Pau and de Castelnau, commanding the armies of Alsace and Lorraine respectively, ordered a general advance on the 10th. At first it met with success: the chief passes of the Vosges from Mt. Donon on the north to the Belfort gap were seized; counter-thrusts by the Germans towards Spincourt and Blamont in the plain of Lorraine were parried; Thann was captured, Mulhouse was re-occupied, and the Germans looked like losing Alsace as far north as Colmar. German Lorraine seemed equally insecure, for on the 18th Castelnau's troops were in Saarburg cutting the rail and roads between Strassburg and Metz. The Germans, however, were not unprepared: their Fifth Army, under the Crown Prince Rupprecht of Bavaria, came down from Metz and fell upon the exposed French left, which was routed with great losses in guns and prisoners on the 21st. Not only did the invasion collapse, but the Bavarians pushed across the French frontier nearly as far as Toul and occupied Lunéville, compelling also a French retreat from the passes of the Vosges. General Pau had soon to follow suit and retire again from Mulhouse and all but the south-west corner of Alsace.