These aims it was sought to effect by means of a series of circular railways, or "rings" of railways, joining up the existing lines, and allowing of the transfer of military transport from one to the other without coming into Paris at all. An "inner" circular railway ("Chemin de Fer de Petite Ceinture") had already been constructed within the fortifications prior to 1870, and this was followed in 1879 by an "outer" line, ("Chemin de Fer de Grande Ceinture"), which provided a wider circle at an average distance of about 20 km. (12½ miles) and established direct rail connection, not only between a large number of the more remote suburbs, together with the different trunk lines at a greater distance from the city, but, also, between the various forts constructed for the defence of Paris.
These circular railways were, in turn, succeeded by a series of connecting links which ensured the provision of a complete ring of rail communication at a still greater distance around Paris, the towns comprised therein including Rouen, Amiens, La Fère, Laon, Reims, Chalons-sur-Marne, Troyes, Sens, Montargis, Orléans, Dreux, and so on back to Rouen. Within, again, this outermost ring there was provided a further series of lines which, by linking up Orléans, Malesherbes, Montereau, Nogent, Epernay, Soissons, Beauvais and Dreux, established additional connections between all the lines from Paris to the north and the east of France, and gave increased facilities for the distribution in those directions of troops arriving at Orléans from the south-west, this being once more done without any need for their entering Paris or even approaching it at a closer distance than about forty miles.
Orléans itself was recognised as a point of great strategical importance in regard to the movement of troops, and it was, accordingly, provided with a number of new lines radiating therefrom, and establishing better connections with other lines. Tours and other centres of military significance, from the same point of view, were strengthened in a like manner. At important junctions, and notably so in the case of Troyes (Champagne), loop lines were built in order that troop trains could be transferred direct from one line to another without stopping, and with no need for shunting or for changing the position of the engine.
In the direction of the eastern frontier the line from Verdun to Metz was completed, and by 1899 the three routes which could alone be made use of in 1870-71 had been increased to ten. Most of them were provided with double-track throughout, and all of them were independent of one another, though having intercommunication by means of cross lines.
Other new railways established connection with or between the forts on both the eastern and the northern frontiers. Others, again, provided direct communication between different harbours or between each of them and strategical points in the interior, thus contributing to the possibilities of their defence in case of attack from the sea. Still others were designed for the defence of the French Alps.
Apart from the provision of all these new lines, much was done in the doubling or even the quadrupling of existing track wherever the question of military transport came into consideration at all. Then at railway stations near to arsenals, and at important strategical centres, specially long platforms were provided to allow of the rapid entraining of men or material in case of need.
While, also, so much was being done for the improvement of the French railway system from an avowedly strategical point of view, there were many additional lines constructed or improvements made which, although designed to further the interests of trade and travel, also added to the sum total of available facilities for military transport.
The advantages specially aimed at were (1) the ensuring of a more rapid mobilisation of troops through the betterment of cross-country connections; (2) the avoidance of congestion of traffic in Paris; (3) the securing of a more rapid concentration on the frontiers, especially when each Army Corps could be assured the independent use of a double-track line of rails for its own use; and (4) the more effective defence of all vital points.
National defence, rather than the building of strategical lines designed to serve "aggressive" purposes, was the fundamental principle on which the policy thus followed since 1870-71 was based; and if, as Captain Pernot wrote in 1894, everything was even then ready for all emergencies, the continuous additions and improvements made since that time, bringing the railway system of the country more and more into harmony with the "perfectionnement" aimed at by France in the organisation of her military transport, must have made the conditions of preparedness still more complete by 1914.