The capitulation of Sedan settles the fate of the last French army in the field. It settles at the same time the fate of Metz and Bazaine’s army; relief being now out of the question, they will have to capitulate too, perhaps this week, almost certainly not later than next week.

There remains the colossal entrenched camp of Paris, the last hope of France. The fortifications of Paris form the hugest complex of military engineering works ever constructed; they have never yet been put to the test, and consequently opinions as to their value are not only divided, but absolutely contradictory. By examining the actual facts of the case, we shall gain a safe basis upon which to found our conclusions.

Montalembert, a French cavalry officer, but a military engineer of uncommon and, perhaps, unparalleled genius, was the first to propose and work out during the latter half of the eighteenth century the plan of surrounding fortresses by detached forts at such a distance as to shelter the place Itself from bombardment. Before him the outworks — citadels, lunettes, &c. — were more or less attached to the enceinte or rampart of the place, scarcely ever farther distant from it than the foot of the glacis. He proposed forts large and strong enough to hold out a separate siege, and distant from the ramparts of the town from six hundred to twelve hundred yards, and even more. The new theory was for years treated with contempt in France, while it found willing pupils in Germany when, after 1815, the line of the Rhine had to be fortified. Cologne, Coblenz, Mayence, and later on Ulm, Rastatt, and Germersheim, were surrounded with detached forts; the proposals of Montalembert were modified by Aster and others, and a new system of fortifications thus arose, known under the name of the German school. By-and-by the French began to see the utility of detached forts, and, when Paris was fortified, it was at once evident that the immense line of ramparts round that city would not be worth constructing unless covered by detached forts, otherwise a breach effected in one place of the rampart would bring on the fall of the whole.

Modern warfare has shown in more than one instance the value of such entrenched camps, formed by a circle of detached forts, with the main fortress for its nucleus. Mantua, by its position, was an entrenched camp, so was Dantzic, more or less, in 1807, and these two were the only fortresses which ever arrested Napoleon I. Again, in 1813, Dantzic was enabled by its detached forts — field works for the most part — to offer a prolonged resistance. The whole of Radetzky’s campaign in 1849 in Lombardy hinged on the entrenched camp of Verona, itself the nucleus of the celebrated Quadrilateral, so did the whole of the Crimean war depend on the fate of the entrenched camp of Sebastopol, which held out so long merely because the Allies were unable to invest it on all sides, and cut off supplies and reinforcements from the besieged.

The case of Sebastopol is, for our purpose, most in point, because the extent of the fortified place was larger than in any previous instance. But Paris is much larger even than Sebastopol. The circuit of the forts measures about twenty-four miles. Will the strength of the place be increased in proportion?

The works of themselves are models of their kind. They are of the utmost simplicity; a plain enceinte of bastions, without even a single demi-lune before the curtains, the forts, mostly bastioned quadrangles or pentagons, without any demi-lunes or other outworks; here and there a horn-work or crown-work to cover an outlying space of high ground. They are constructed not so much for passive as for active defence. The garrison of Paris is expected to come out into the open, to use the forts as supporting points for its flanks, and by constant sallies on a large scale to render impossible a regular siege of any two or three forts. Thus, whilst the forts protect the garrison of the town from a too near approach of the enemy, the garrison will have to protect the forts from siege batteries; it will have constantly to destroy the besiegers’ works. Let us add that the distance of the forts from the ramparts precludes the possibility of an effective bombardment of the town until two or three at least of the forts shall have been taken. Let us further add that the position, at the junction of the Seine and Marne, both with extremely winding courses, and with a strong range of hills on the most exposed, the north-eastern front, offers great natural advantages, which have been made the best of in the planning of the works.

If these conditions can be fulfilled, and the two million people inside can be regularly fed, Paris is undoubtedly an extremely strong place. To procure provisions for the inhabitants is not a very difficult matter, if taken in hand in time, and carried out systematically. Whether that has been done in the present instance is very doubtful. What has been done by the late Government looks like spasmodic and even thoughtless work. The accumulation of live cattle without provender for them was a perfect piece of absurdity. We may presume that, if the Germans act with their usual decision, they will find Paris but poorly provisioned for a long siege.

But how about that chief condition, the active defence, the garrison which goes out to attack the enemy, instead of striking behind the ramparts? To show the full strength of Its works, and to prevent the enemy from taking advantage of its weakness, the absence of protecting outworks in the main ditches, Paris requires to count among its defenders a regular army. And that was the fundamental idea with the men who planned the works; that a defeated French army, its inability to hold the field being once established, should fall back upon Paris, and participate in the defence of the capital; either directly, as a garrison strong enough to prevent, by constant attacks, a regular siege and even a complete investment, or indirectly, by taking up a position behind the Loire, there recruiting its strength, and then falling, as opportunities might offer, upon such weak points as the besiegers, in their immense investing line, could not avoid presenting.

Now, the whole conduct of the French commanders in this war has contributed to deprive Paris of this one essential condition of its defence. There are of all the French army but the troops which remained in Paris and the corps of General Vinoy (the 13th, originally Trochu’s); together, perhaps, 50,000 men, almost all, if not indeed all of them, fourth battalions and Mobile Guards. To these may be added perhaps 20,000 or 30,000 men more of fourth battalions, and an indefinite number of Mobile Guards of the provinces, raw levies totally unfit for the field. We have seen at Sedan what little use such troops are in a battle. They, no doubt, will be more trustworthy when they have forts to fall back upon, and a few weeks’ drill, discipline, and fighting will certainly improve them. But the active defence of a large place like Paris implies movements of large masses in the open, regular battles at a distance in front of the sheltering forts, attempts to break through the line of investment or to prevent its completion. And for that, for attacks on a superior enemy, where surprise and dash are required, and where the troops must be kept perfectly in hand for that purpose, the present garrison of Paris will be scarcely available.

We suppose the united Third and Fourth German armies, fully 180,000 strong, will appear before Paris in the course of next week, surround it with flying columns of cavalry, destroy the railway communications, and thereby all chance of extensive supplies, and prepare the regular investment, which will be completed on the arrival of the First and Second armies after the fall of Metz, leaving plenty of men to be sent beyond the Loire to scour the country, and prevent any attempt at the formation of a new French army. Should Paris not surrender, then the regular siege will have to begin, and, in the absence of an active defence, must proceed comparatively rapidly. This would be the regular course of things if there were none but military considerations; but affairs have now come to a point when these may be set aside by political events, to prognosticate which does not belong to our province here.