兵不厌诈（兵不厭詐）　

◎ 兵不厌诈 bīngbùyànzhà

[all is fair in war;nothing is too deceitful in warcraft] 兵:军事、战争;不厌:不嫌;诈:欺骗、谋术。用兵作战可以无限制地用计谋迷惑敌方

事贵应机,兵不厌诈。——《北齐书》