But if the impact of equal forces on the Aisne flattened them out towards the west, it had the same effect in the other direction, though here it was the Germans who took the offensive in trying to penetrate Sarrail's flank on the Meuse and thus get behind the whole front of the Allies. Verdun was the nut to be cracked, but Sarrail had been extending its defences so as to put the city beyond the reach of the German howitzers and surrounding it with miles of trenches and wire-entanglements; and the Germans preferred to attempt another method than frontal attack. About the 20th four new corps, chiefly of Württemburgers, appeared in Lorraine, bringing their forces up to seven against Sarrail's three; and an attack was made on Fort Troyon on the Meuse which reduced it to a dust-heap but failed to carry the Germans across the river. A more serious onslaught was made on the 23rd against St. Mihiel, which was captured while the neighbouring forts of Paroches and the Camp des Romains were destroyed. But again the Germans were prevented from pushing their advantage, and were left with no more than a wonderful salient which looked on the map like Germany putting out its tongue at France and resisted all efforts to repress this insolence until the closing months of the war. Having achieved but a sterile success to the south of Verdun, the Crown Prince encountered a greater failure to the west. On 3 October he attacked Sarrail's centre in the forest of the Argonne, seeking to recapture St. Menehould, the headquarters he had abandoned on 14 September. His troops were caught in La Grurie wood and so badly mauled that they temporarily lost Varennes and the main road through the Argonne to Verdun. Foiled in both these directions, the Germans revenged themselves by bombarding Reims in the centre and ruining its cathedral; "the commonest, ugliest stone," wrote a German general, "placed to mark the burial-place of a German grenadier is a more glorious and perfect monument than all the cathedrals in Europe put together." The bombardment did not help them much; Neuvillette, which they had seized two miles north of Reims, was lost again on 28 September, and the French also recovered Prunay, the German occupation of which had driven a wedge between Foch's and Langle's armies. On the other hand, Berry-au-Bac, where the great road crossed the Aisne and the French often reported progress, remained in German hands for four years longer. Both sides were now firmly entrenched, and their armies were learning that new art of trench warfare which was to tax their ingenuity, test their endurance, and drain their strength, until years later this war of positions once more gave place to a war of movement. The lines had become stabilized, and between Reims and the Alps they did not alter by half a dozen miles at any point from September 1914 until September 1918. The question of October was whether and where they would be fixed between the Aisne and the sea.