The antiquitie many tymes gotte tounes, with muinyng under ground in twoo maners, either thei made a waie under grounde secretely, whiche Risse in the toune, and by thesame entered, in whiche maner the Romaines toke the citee of Veienti, or with the muinyng, thei overthrewe a walle, and made it ruinate: this laste waie is now a daies moste stronge, and maketh, that the citees placed high, be most weake, bicause thei maie better bee under muined: and puttyng after in a Cave of this Gunne pouder, whiche in a momente kindelyng, not onely ruinateth a wall, but it openeth the hilles, and utterly dissolveth the strength of them.
"Machiavelli, Volume I The Art of War; and The Prince"
Niccolò Machiavelli