The Bishop of Strasburg came out to the outposts at Schiltigheim to entreat forbearance for the citizens. Much as damage to this German city was to be regretted, since the Prelate was not empowered to negotiate the bombardment was continued through the night of the 25th, when it reached its height. But the headquarter staff at Mundolsheim became convinced that this mode of attack would not accomplish the desired object, and that the more deliberate course of a regular siege would have to be resorted to. General von Mertens was placed in charge of the engineer operations, General Decker was given the direction of the artillery.
During the night of the 29th--30th August the first parallel was opened very close to the glacis, and soon was prolonged from the Rhine and Marne canal, through the churchyard of St. Helena, to the Jewish cemetery at Königshofen.
The number of batteries on the left bank of the Rhine was soon increased to 21, on the right bank to 4; so that 124 guns of the heaviest calibre were ready in protected positions to begin the contest with the guns of the fortress. The further offensive operations were directed against bastions Nos. 11 and 12 on the north-west salient of the fortress. In the night of September 1st--2nd the second parallel was completed, but not without opposition. A strong sortie of fourteen companies of the garrison made at daybreak (of 2nd) upon the island of Waken, and in front of Kronenburg and Königshofen, was repulsed.
The fortress then opened a heavy fire, pouring such a storm of projectiles on the siege-works that they had to be abandoned, till at about nine o'clock the artillery of the attack had silenced the guns of the fortress. A second sortie followed on the 3rd September, which was not repulsed before it had reached the second parallel.
A short truce was granted at the request of the commandant, to allow of the burial of the dead lying in front of the works. And on this day a grand salvo announced to the besieged the victory of Sedan.
Incessant rain had filled the trenches of the second parallel, 2400 paces in length, ankle-deep with water, and it was not till the 9th that they were completely repaired. Five batteries were moved forward from the first parallel, as special batteries were required to crush the fire of lunette No. 44, which took in flank all the approaches. These soon silenced its guns, and the lunette was abandoned by the garrison.