coup de main or coups de main

French expression which literally means "stroke of the hand"; coup stroke , de  of , main hand. In English it means a surprise action, usually to take the initiative away from an enemy or opponent. Especially used as a military term, but not exclusively so. In Oxford English Dictonary since 1758

Example: "In a coup de main, DMan's account was frozen and his most aggressive nodes deleted."

This is an entry in the mini series about French idioms in the English language.