"Knife Behind Back"

"Knife Behind Back" is an idiom that describes a situation where someone betrays or harms another person in a sneaky or untrustworthy way, often through deception or underhanded actions. It implies a breach of confidence or loyalty, typically occurring without the victim’s awareness until the damage is done. This phrase captures the idea of treachery happening discreetly, similar to stabbing someone in the back, and highlights the importance of trust and honesty in relationships or alliances.