Notwithstanding the advantage thus gained, the practical benefits secured by the Germans, although important in their effect on the final issue, were far from being as great as the Army leaders may have anticipated or desired. The destruction work carried out by the French on their own railways, on their retirement, was much more serious than anything experienced in the Prussian campaign in Austria. Thus the works for the re-establishment of the Paris-Strasburg line (of primary importance to the Germans for the siege of Paris) extended from September 17 to November 22. The French had blocked the tunnel of Nanteuil by the explosion therein of six mines which brought down the walls and filled the western end of the tunnel with about 4,000 square yards of sand. Attempts to clear away the obstruction were a failure, owing to the occurrence of fresh slips due to the wet weather, and eventually the Construction Corps built a loop line which avoided the tunnel, and so restored communication. The defence of some of the principal lines by fortresses also contributed to the difficulties of the invaders; though, on the other hand, these difficulties would have been greater still if the French had always adopted the best and most scientific methods of interrupting rail communications, as, presumably, they would have done if they had had the advantage of a well-organised corps prepared in advance for the work that required to be done. At Fontenoy-sur-Moselle, between Nancy and Toul, there was, for example, a bridge of seven arches, effective destruction of which would have made a very serious check in the communications along the principal line between Germany and Paris; but, instead of blowing up the bridge in the middle, the men entrusted with the work (in January, 1871) brought down two arches at the side of the bridge, causing a break which the Germans were able to fill in with stones and earth, restoring communication in about seventeen days. Then, although several of the tunnels in the Vosges mountains were mined, the mines had not been charged, and before instructions to blow up the tunnels had been received by those awaiting them, the Germans were on the spot and took possession. On the other hand the absence on the side of the French of an organised corps for destruction as well as construction did not prevent the carrying out of some very bold and highly successful work by parties of _franc tireurs_, who showed alike their appreciation of the importance of rail communications and their skill in impeding them. One especially striking feat in this direction was accomplished by a company known as the "Franc Tireurs of the Meuse."