How the reconnaissance of a line which might have been subjected to the enemy's destructive tactics was carried out is thus told by Captain C. E. Webber, R.E., in his "Notes on the Campaign in Bohemia in 1866":—
The reconnaissance starts with, and, until interrupted, keeps up with, the advance guard, the movement being covered by cavalry scouts on each side of the line.
The greater portion of the train in charge of the department, with one engine in front and another behind, advances slowly, preceded at a distance of about 500 paces by a trolley carrying one of the officers, four men to work it, and a bugler. On arriving at any obstruction the trolley signals to the train by bugle and extra caution is used in advancing towards it. If in presence of the enemy, the scouts give warning to the officer in the trolley, who returns to the train and the whole retires. The second engine can be detached from the rear to send messages or bring up fresh supplies.
But for the successes already gained in the same direction by the Federals in the United States, the speed with which repairs were carried out by the Prussian Construction Corps—then so recently organised—would have been regarded as remarkable. In various instances communication was restored within from one and a half to three days after the destruction even of important bridges.
As it happened, however, whilst the Austrians had shown an excess of zeal in some directions by destroying bridges when the tearing up of the rails would have answered the same purpose, the hesitation of the responsible Austrian officer to fire the mines which had already been laid to the bridge over the Elbe at Lobkowitz was of great advantage to the Prussians, leaving them the use of the line from Turnau to Prague, Pardubitz and Brünn between July 18 and July 27, on which latter date the bridge was at last destroyed by order of the governor of Theresienstadt. This particular bridge was one of exceptional strategical importance, and, according to Captain Webber, the construction even of a temporary substitute—had the Austrians blown up the bridge before the Prussians could cross it—would have taken no less than six weeks. The omission, also, of the Austrians to remove or to destroy the railway rolling stock they left behind at Prague, on their retirement from that city, conferred a further benefit on the Prussians. These examples would seem to show that promptness in carrying out destruction at a critical moment may be no less important on the one side than efficient organisation on the other for accomplishing the work of restoration in the shortest possible time.
While the Construction Corps had thus fully justified its existence, the sudden creation of such a corps for the purposes of a particular war, and for the period of the war only, was considered inadequate for a country where a large standing Army had to be maintained in readiness for action at any moment, in case of need. Hence it was thought desirable that Prussia should have a Field Railway Section established on a permanent and well-organised footing. There was the further reason for adopting this course because the Pioneers, composed almost exclusively of reservists, had received no special training in railway work, while the railway men themselves, accustomed to building lines in a solid way for public use, were at a disadvantage when called on to carry out, with great rapidity, and in a rough and ready manner, work that was wanted only to serve the temporary purposes of the Army with which they were associated.
It was found, also, that the corps, comprising so large a civil element, had escaped the supervision and control of the Executive Commission at Berlin which had for its function the regulation of all matters concerning military rail-transport. Nor did the Construction and Destruction Corps constitute, as well, an Operation Corps, providing for the working of railways at the theatre of war, and especially of railways taken from the enemy. The Prussians had, indeed, been able to command the services of Austrian railwaymen in working the railways seized in that country; but there was no certainty that the adoption of a like expedient would be possible in any future war.
By this time the whole subject of the destruction and restoration of railway lines as an important element in modern warfare was attracting attention among military authorities and writers in Germany. A translation of McCallum's report was published, and the issue was begun of what was to develop into a long series of technical papers, pamphlets or books—such as, for example, Wilhelm Basson's "Die Eisenbahnen im Kriege, nach den Erfahrungen des letzten Feldzuges" (Ratibor, 1867)—dealing with the art of rapidly destroying and restoring railways in time of war and the most effective measures to be adopted in the attainment of either end.
These various considerations and developments were, no doubt, the reason for the issuing, on August 10, 1869, of a Prussian Royal Decree which created a permanent cadre of Railway Troops to be constituted of Pioneers who were to undergo regular instruction in everything relating to the construction, destruction and operation of railways. A new Battalion of Pioneers was to be raised for the purpose, and the whole scheme was to be carried into effect in the course of 1871.
When, in 1870, the war with France broke out, the preparations for the creation of this permanent corps were still proceeding; but the Prussians were, nevertheless, able to enter on the campaign with four sections of Railway Troops, subsequently increased to six, including one Bavarian section. Each section comprised Engineers, Pioneers, railwaymen and auxiliary helpers, all of whom wore a uniform having the letter "E" ("Eisenbahntruppen") on the shoulder, and carried rifles. Prussia, in fact, once more started, as in 1866, with such advantage over her enemy as might result from her control of a Railway Construction Corps. At the outset France had no similar body, and though, during the progress of the war, she hurriedly set about the creation of a Construction Corps of her own, that corps did not do very much beyond collecting at Metz and Strasburg a great store of railway materials which was afterwards to fall into the hands of the Prussians, and assist them in their own operations.
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.