Their way to Paris lay open but for two last perilous and endangered defences; to the right the lines of Weissembourg, to the left Maubeuge.
There are two avenues of approach westward into the heart of Gaul and two only. The great marches of the French eastward, which are the recurrent flood-tides of European history, pour up by every channel, cross the Alps at every pass, utilise the narrow gate of Belfort, the narrower gate of the Rhone, the gorge of the Meuse, the Cerdagne, the Somport, Roncesvalles. But in the ebb, when the outer peoples of Europe attempt invasion, two large ways alone satisfy that necessity at once for concentration and for a wide front which is essential to any attack upon a people permanently warlike.[[35]] These two ways pass, the one between the Vosges and the Ardennes, the other between the Ardennes and the sea. By the first of these have come hosts from Attila’s to those of 1870; by the second, hosts from the little war-band of Clovis to the Allies of 1815. Both avenues were involved in this balancing moment of ’93: the first, the passage by Lorraine, was still blocked by the defence of Mayence and the lines of Weissembourg;[[36]] the second, the passage by the Low Countries, was all but won. Of the string of fortresses defending that passage, Maubeuge was now almost the last, would soon be the very last, to stand.
[35]. These words “concentration” and “a wide front” may seem self-contradictory. I mean by concentration a massed invasion, if you are to succeed against a military people; and by “a wide front” the necessity for attacking such a people in several places at once, if you are to succeed. For a force marching by a single narrow gate (such as is the valley of the Meuse) is in peril of destruction if its opponents are used to war.
[36]. The lines of Weissembourg did not, of course, physically block the entry; they lay on the flank of it: but until the army behind them could be dislodged it made impossible an advance by that way into Lorraine.
It was not upon Mayence and the lines of Weissembourg (though these to soldiers seemed of equal importance), it was upon the bare plains of the north that Paris strained its eyes in these perilous hot days—the long flat frontier of Hainault and of Flanders—and it is here that the reader must look for his background to the last agony of the Queen.
The line of defence, stretched like a chain across that long flat frontier, was breaking down, had almost disappeared. Point after point upon the line had gone; it held now by one point remaining, and the ruin of that was imminent: the Republicans were attentive, in a fever for the final crash, when the last pin-point upon which the defence was stretched should give way and the weight of the invaders should pour unresisted upon Paris. When that march began there would be nothing for those who had challenged the world but “to cover their faces and to die.”
Of what character is that north-eastern frontier of France and what in military terms was the nature of the blow which was about to fall?
It is a frontier drawn irregularly due south-east for a hundred miles, from the sea to the difficult highlands of Ardennes and the waste Fagne Land. As it runs thus irregularly, it cuts arbitrarily through a belt of population which is one in creed, speech, and tradition: there is therefore no moral obstacle present to the crossing of it, and to this moral facility of passage is added the material facility that no evident gates or narrows constrain an invading army to particular entries. From the dead flat of the sea-coast the country rises slowly into little easy hills and slopes of some confusion, but not till that frontier reaches and abuts against the Ardennes does any obstacle mark it. It is traversed by a score of main roads suitable for a parallel advance, all excellent in surface and in bridges and other artifice; it is thickly set with towns and villages to afford repose and supply. Lastly, it is the nearest point of attack to Paris. Once forced, ten days’ rapid marching from that frontier brings the invader to the capital, and there is nothing between.
Such advantages—which, it is said, tempt unstable brains in Berlin to-day—have rendered this line, whenever some powerful enemy held its further side, of supreme defensive importance to the French. Until the formation of the Belgian State it had been for centuries—from the battle of Bouvines at least—the front of national defence; here the tradition of the seventeenth century and the genius of Vauban and his successors had established a network of strongholds, which formed the barrier now so nearly destroyed in this summer of ’93.
These fortresses ran along that frontier closely interdependent, every one a support to its neighbours, forming a narrowing wedge of strongholds, from where Dunkirk upon the sea was supported by Gravelines to where the whole system came to a point in the last fortress and camp of Maubeuge, close up against the impassable Ardennes.