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From the Hadith:
Bukhari (52:269) - "The Prophet said, 'War is deceit.'" The context of this is thought to be the murder of Usayr ibn Zarim and his thirty unarmed men by Muhammad's men after he "guaranteed" them safe passage (see Additional Notes below).
Bukhari (49:857) - "He who makes peace between the people by inventing good information or saying good things, is not a liar." Lying is permitted when the end justifies the means.
Bukhari (84:64-65) - Speaking from a position of power at the time, Ali confirms that lying is permissible in order to deceive an "enemy."
Muslim (32:6303) - "...he did not hear that exemption was granted in anything what the people speak as lie but in three cases: in battle, for bringing reconciliation amongst persons and the narration of the words of the husband to his wife, and the narration of the words of a wife to her husband (in a twisted form in order to bring reconciliation between them)."
Bukhari (50:369) - Recounts the murder of a poet, Ka'b bin al-Ashraf, at Muhammad's insistence. The men who volunteered for the assassination used dishonesty to gain Ka'b's trust, pretending that they had turned against Muhammad. This drew the victim out of his fortress, whereupon he was brutally slaughtered despite putting up a ferocious struggle for his life.
by contrast here’s Thomas Aquinas talking about the rules of war:
Now a man may be deceived by another’s word or deed in two ways. First, through being told something false, or through the breaking of a promise, and this is always unlawful. No one ought to deceive the enemy in this way, for there are certain “rights of war and covenants, which ought to be observed even among enemies,” as Ambrose states (De Officiis i).
Summa Theologica > Second Part of the Second Part > Question 40 > Article 3
http://www.newadvent.org/summa/3040.htm