1852-1870 - Second EmpireFortifications
In old times France was uncommonly rich in fortresses ; new ones were constantly built, and still the old ones were not allowed to decay. Until the reign of Louis Philippe, the French system of fortresses was essentially a cordon system, according to the theory of the triple girdle, and then under his government it was reduced to a network, with Paris as the center.
In spite of the appearance, in 1859, of the artillery with rifled canons and a little later of the cylindrical - ogival shell, the military engineers of the Second Empire remained faithful to the concept of bastioned fortification. Under the impulse of the young military chiefs of that time and in particular of the lieutenant-colonel Séré de Rivières, commanding the Royal Engineers, Napoleon III thus decided to fill the interstitial gaps between the citadels, by a "defensive curtain" made up of "detached forts". In Metz in 1867 Séré de Rivières organizes the construction of four "detached forts", in order to transform this fortified place in a vast entrenched camp that the enemy will not dare to defy.
In the year 1868 France had 88 proper fortresses, and 47 strong places (towns with old fortifications, isolated forts, and old castles). To keep this mass of fortified places in repair required a large expenditure of money, and this prevented much thought being given to the erection of new works. Under the Second Empire, with the increase in the price of all things, and also of building materials, the difficulty of constructing them increased also. Moreover, from the time of the Crimean war until shortly after the Italian campaign, Napoleon III. stood as the recognised arbiter and umpire of Europe. Therefore, considering the behaviour of the whole Continent, and the state of affairs in Germany, the French cannot be blamed if they believed ever more and more firmly that no cannon-shot could be fired without their permission ; that circumstances might, indeed, compel France to attack, but that she could never be exposed to be herself attacked.
Consequently, even the introduction of rifled guns into warfare did not at first cause the Government to occupy itself seriously with the question of the fortresses. It was only in the years 1863 and 1864 that the faith of the French Government on their decided ascendancy began somewhat to waver, and then first some works of improvement were undertaken on the more important fortresses with a view to covering better the masonry buildings, especially the powder-magazines, and of providing bomb-proof shelter for the garrison, ammunition, and supplies.
The works, by reason of the outlay which they occasioned, naturally led to the question, Whether it would not be more serviceable to give up completely a number of small places which were acknowledged to be useless, so that more money could be expended upon the remaining fortresses ? This question was answered in the affirmative ; and by a decree of the 26th of June 1867, many places were completely abandoned as strongholds, and others were reserved, only to be used, in case of war, as fortresses in a partial way. The places given up belonged mostly to the fourth class, which for a long time had been of no military importance. Among those of the second and third class which were allowed to decay were Weissenburg, Boulogne, Lauterburg, and Carcassonne.
New works were especially undertaken from the beginning of 1868 on the strong places in the east. Particular attention was paid to Metz, Belfort, and Langres; while at Strasburg only improvements on the existing works were made, but these, it is true, on a very extensive scale. We propose, as soon as any one fortress begins to play a part in the history of the war of 1870, to describe its fortifications more minutely, and to give a military picture of their connection with one another, explaining the main idea on which they were planned, and the circumstances which exercised an influence upon the carrying out of this idea.
But in 1870, these detached forts are encircled by the Prussian army. In the Franco-German War of 1870-71 French fortresses exercised a capital influence on both the strategical and the tactical developments. They rendered services of the highest importance to the French, but at the same time they exercised an irresistible and injurious force of attraction upon the French commanders and even upon the men.
They did not have this influence upon the Prussians. Von Moltke did not concern himself overmuch with fortified places. He left detachments to besiege them, but he moved on with the main force. Paris was besieged in force not because it was a fortified place but because it was the capital and the heart of France. And von Moltke was prepared to withdraw the bulk of the besieging forces from Paris if that course had become necessary in order to meet new armies in the field.
While the entrance of the German army upon French territory was easily accomplished, owing to its superiority in numbers, organization, and rapid mobilization at the first stage of the war, it was necessary to detach from the advancing army the large forces investing Metz, Strasburer, Belfort, and other fortified places. These forces, with their artillery, were occupied from 30 to 100 days in reducmg these strong places, which were upon their lines of communication and could not be neglected. The fortifications of Paris, although their scarp walls were exposed and their casemates not strong enough to resist the German artillery, held the German army in check from the middle of September until the end of January, affording four and one half months for the organization of an army of relief in the other parts of France.
By a smart and skilful encircling manoeuvre, they stopped the army of Marshall Bazaine in "place de Metz". One striking feature of this short war was the failed French defense of the major fortress of Metz, located near the Franco-Prussian border. The relatively rapid German capture of this forward position with its large, but isolated, defending force impressed itself deeply on the French military. The loss of Bazaine's army at Metz was a notable illustration of the baleful attraction exercised by a fortress. Political conditions entered into the problem, as a continued retreat meant the abandonment of large areas of the soil of France to the invader. The correct use of the fortress would have been made by occupying it with a small fraction of the army, delaying the enemy, forcing him to make a detachment to observe the fortress, and thereby gaining time for the main force to continue the retreat and receive reinforcements.
The army of the Emperor was encircled by the Prussian army in Sedan. One important service rendered by the fortresses was the blocking of a number of railroad lines which would have been of great value to the Prussians. The importance of the fortresses to the French would have been much increased if they had been better prepared and better defended.
The defeat of 1871 forced the very young Republic to sign the treaty of Frankfurt and to accept the annexation of Alsace and Moselle to the german empire. On several hundred kilometers, between Longwy and Belfort, the fortified barrier, designed by Vauban iwa destroyed. The road toward Paris was consequently wide open.
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