Again in 1815, Napoleon, even after the defeat of Waterloo, possessed lines of defence sufficiently strong to resist all attempts at invasion.  But again the want of co-operation on the part of the government at Paris, and the treason of his own generals, forced his second abdication.  If he had retained the command of the army, and the nation had seconded his efforts, the allies would never have reached Paris.  But the new government presented the disgraceful spectacle of opening the way for the enemies of their country.  “France,” said Napoleon, “will eternally reproach the ministry with having forced her whole people to pass under the Caudine-forks, by ordering the disbanding of an army that had for twenty-five years been its country’s glory, and by giving up to our astonished enemies our still invincible fortresses.”

History fully supports Napoleon’s opinion of the great danger of penetrating far into a hostile country to attack the capital, even when that capital is without fortifications.  The fatal effects of such an advance, without properly securing the means of retreat, is exemplified by his own campaign of 1812, in Russia.  If, after the fall of Smolensk, he had fortified that place and Vitepsk, which by their position closed the narrow passage comprised between the Dnieper and the Dwina, he might in all probability, on the following spring, have been able to seize upon Moscow and St. Petersburg.  But leaving the hostile army of Tschkokoff in his rear, he pushed on to Moscow, and when the conflagration of that city cut off his hopes of winter quarters there, and the premature rigor of the season destroyed the horses of his artillery and provision-trains, retreat became impossible, and the awful fate of his immense army was closed by scenes of horror to which there is scarcely a parallel in history.  This point might be still further illustrated by the Russian campaign of Charles XII., in 1708-9, the fatal advance of the French army on Lisbon, in the Peninsular war, and other examples of the same character.

Even single works sometimes effect the object of lines of fortifications, and frustrate the operations of an entire army.  Thus, Lille suspended for a whole year the operations of Prince Eugene and Marlborough; the siege of Landrecies gave Villars an opportunity of changing the fortunes of the war; Pavia, in 1525, lost France her monarch, the flower of her nobility, and her Italian conquests; Metz, in 1552, arrested the entire power of Charles V., and saved France from destruction; Prague, in 1757, brought the greatest warrior of his age to the brink of ruin; St. Jean d’Acre, in 1799, stopped the successful career of Napoleon; Burgos, in 1812, saved the beaten army of Portugal, enabled them to collect their scattered forces, and regain the ascendancy; Strasburg has often been, the bulwark of the French against Germany, saving France from invasion, and perhaps subjugation.

In nearly the language of Napoleon, (Memoirs, vol.  IX.,) If Vienna had been fortified in 1805, the battle of Ulm would not have decided the fate of the war.  Again, in 1809, if this capital had been fortified, it would have enabled the Archduke Charles, after the disaster of Eckmuhl, by a forced retreat on the left of the Danube, to form a junction with the forces of General Hiller and the Archduke John.