Meanwhile the Germans were making ready a weighty enterprise. The muster of the huge Third Army to the north of Alsace enabled their General Staff to fix August 4 for a general advance against that frontier. It fell to this army, under the Crown Prince of Prussia, Frederick William, to strike the first great blow. Early on August 4 a strong Bavarian division advanced against the small fortified town of Weissenburg, which lies deep down in the valley of the Lauter, surrounded by lofty hills. There it surprised a weak French division, the vanguard of MacMahon's army, commanded by General Abel Douay, whose scouts had found no trace of the advancing enemy. About 10 A.M. Douay fell, mortally wounded; another German division, working round the town to the east, carried the strong position of the Geisberg; and these combined efforts, frontal and on the flank, forced the French hastily to retreat westwards over the hills to Wörth, after losing more than 2000 men. The news of this reverse and of the large German forces ready to pour into the north of Alsace led the Emperor to order the 7th French corps at Belfort, and the 5th in and around Bitsch, to send reinforcements to MacMahon, whose main force held the steep and wooded hills between the villages of Wörth, Fröschweiler, and Reichshofen. The line of railway between Strassburg and Bitsch touches Reichshofen; but, for some reason that has never been satisfactorily explained, MacMahon was able to draw up only one division from the side of Strassburg and Belfort, and not one from Bitsch, which was within an easy march. The fact seems to be that de Failly, in command at Bitsch, was a prey to conflicting orders from Metz, and therefore failed to bring up the 5th corps as he should have done. MacMahon's cavalry was also very defective in scouting, and he knew nothing as to the strength of the forces rapidly drawing near from Weissenburg and the east.