VII. When diplomacy and subversion are not enough and fighting is unavoidable, use methods and tactics that exploit enemy weaknesses, avoid consuming combat forces, and patiently whittle down the enemy's strength. This might require much time. But there is no urgency because as soon as one enemy is no more, another will surely take his place. All is constantly changing as rulers and nations rise and fall. Only the empire is eternal -- if, that is, it does not exhaust itself.