Soissons still hindered the further utilization of the railway, which had been re-opened at the time of the fall of Toul as far as Rheims. This fortress had been bombarded by field artillery without success when the Army of the Meuse passed by it on the march to Paris, and since then it had only been kept under observation until on October 6th eight Landwehr battalions, four squadrons, two batteries, two companies of pioneers, and four of fortress artillery made good the investment.

Soissons, with its walls about 26 feet high, had complete immunity from escalade, and the damming of the Crise brook made it unassailable on the south. The south-west front, on the other hand, had only a dry ditch, with no counterscarp of masonry; here, too, the town was commanded by Mont Marion, rising to a height of 300 feet at a distance of little more than a mile. Against this face of the fortress, therefore, the artillery attack was directed at short range, when on the 11th October there arrived from Toul 26 Prussian siege-guns with 170 rounds for each, and 10 French mortars. The Grand Duke of Mecklenburg took over the command.

In a clear moonlight night the artillery with the help of the infantry was brought up on to the heights of Ste. GeneviÈve; the construction of the batteries about Belleu and in Mont Marion was completed and the arming of them effected. At six in the morning of 12th October they opened fire simultaneously.

The besieged answered with great spirit but with small results, and the accurate fire of the Prussian artillery soon subdued that of the enemy in the particular front.

A narrow breach was visible by next day, and the fire from the fortress was evidently much enfeebled; but the commandant decidedly rejected the demand that he should capitulate. On the 14th he increased the number of guns on his south front, so that the batteries on Ste. GeneviÈve had an arduous struggle. The French also laboured hard along the front of the attack to restore the severely damaged works, brought more guns up to the ramparts, and closed the breach by retrenchment.

But on the 15th these repairs were soon demolished again by the artillery of the attack, and a breach was made 40 paces wide and amply spread with earth. As the fortress still kept up a brisk fire, it was determined to bring up the field-batteries within 900 paces. But at eight in the evening, when this operation was just begun, the commandant opened negotiations and surrendered the place on the Sedan terms. The garrison marched out next morning, for the most part drunk. A thousand Gardes-Mobiles were dismissed on parole, 3800 regulars were made prisoners.

The attack had cost 120 men; 128 guns and 8000 small arms became prize of war, besides vast stores of provisions.