Note 59 — Chapter X · MARLBOROUGH

The famous lines of Torres Vedras are the only instance in more modern times of such a method of defence proving successful, and they could not, from the nature of the case, be turned, and were never assailed. The system on which the eastern frontier of France is now defended is an instance of the same thing on the greatest possible scale. There the flanks abut on neutral countries, and cannot therefore be turned without violating the neutrality of either Belgium or Switzerland. What it would cost to break through such a line cannot be calculated, for it would depend on the effect, as yet untried, of modern scientific developments in explosives, electric communication and the like: but it can hardly be doubted that it could be done, if the assailant were willing to pay the price.