MORASSES, that is, impassable swamps, which are only traversed by a few embankments, present peculiar difficulties to the tactical attack, as we have stated in treating of the defence. Their breadth hardly ever admits of the enemy being driven from the opposite bank by artillery, and of the construction of a roadway across. The strategic consequence is that endeavours are made to avoid attacking them by passing round them. Where the state of culture, as in many low countries, is so great that the means of passing are innumerable, the resistance of the defender is still strong enough relatively, but it is proportionably weakened for an absolute decision, and, therefore, wholly unsuitable for it. On the other hand, if the low land (as in Holland) is aided by inundations, the resistance may become absolute, and defy every attack. This was shown in Holland in the year 1672, when, after the conquest and occupation of all the fortresses outside the margin of the inundation, 50,000 French troops became available, who,—first under Condé and then under Luxemburg,—were unable to force the line of inundation, although it was only defended by about 20,000 men. The campaign of the Prussians, in 1787, under the Duke of Brunswick, against the Dutch, ended, it is true, in a quite contrary way, as these lines were then carried by a force very little superior to the defenders, and with trifling loss; but the reason of that is to be found in the dissensions amongst the defenders from political animosities, and a want of unity in the command, and yet nothing is more certain than that the success of the campaign, that is, the advance through the last line of inundation up to the walls of Amsterdam depended on a point of such extreme nicety that it is impossible to draw any general deduction from this case. The point alluded to was the leaving unguarded the Sea of Haarlem. By means of this, the Duke turned the inundation line, and got in rear of the post of Amselvoen. If the Dutch had had a couple of armed vessels on this lake the duke would never have got to Amsterdam, for he was "au bout de son latin." What influence that might have had on the conclusion of peace does not concern us here, but it is certain that any further question of carrying the last line of inundation would have been put an end to completely.
The winter is, no doubt, the natural enemy of this means of defence, as the French have shown in 1794 and 1795, but it must be a severe winter.
Woods, which are scarcely passable, we have also included amongst the means which afford the defence powerful assistance. If they are of no great depth then the assailant may force his way through by several roads running near one another, and thus reach better ground, for no one point can have any great tactical strength, as we can never suppose a wood as absolutely impassable as a river or a morass.—But when, as in Russia and Poland, a very large tract of country is nearly everywhere covered with wood, and the assailant has not the power of getting beyond it, then, certainly, his situation becomes very embarrassing. We have only to think of the difficulties he must contend with to subsist his army, and how little he can do in the depths of the forest to make his ubiquitous adversary feel his superiority in numbers. Certainly this is one of the worst situations in which the offensive can be placed.