It is an incontestable fact that no kind of fortress, wheresoever placed, however strongly manned, however expensively constructed, and however numerous its garrison, has ever given permanent security to a State-has seldom indeed given it even temporary protection. Moreover, a fortress once invested is certain to fall, unless a relieving field-army can beat the besiegers away. We read in the history of one generation of the "virgin" fortress of Ingoldstadt or of Metz, but when we open the records of another generation, we find that its pride has bitten the dust. In some cases a very small fort in a...