perfidy

noun

1. (countable, uncountable)A state or act of violating faith or allegiance; violation of a promise or vow, or of trust.
2. (countable, uncountable)An illegitimate act of deception, such as using symbols like the Red Cross or white flag in a false claim of surrender to gain proximity to an enemy for purposes of attack.

   “Stratagems must be carefully distinguished strategy from perfidy, since the former are allowed, whereas the latter is prohibited.”

   “Abuse of a protective emblem amounts to perfidy and constitutes a war crime under the customary law of armed conflict.”

   “Ruses of war are legitimate so long as they do not involve treachery or perfidy on the part of the belligerent resorting to them.”

   “Cyberattacks almost inevitably involve an element of deception, such as tricking a user to click on a malicious link. So, to what extent could cyberattacks count as perfidy and therefore be illegal given international humanitarian law?”

3. (countable, uncountable)A state or act of deceit.

   “Germans could not get over the perfidy of it. It was unbelievable that the English, having degenerated to the stage where suffragettes heckled the Prime Minister and defied the police, were going to fight.”

   “Honda Motor Co. is the latest victim of e-mail perfidy, which started when a phony chain letter promised that the automaker would give away free cars.”

   “Letterman roared about the perfidy of lying politicos.”