A preemptive strike is a term for launching an attack on a target before it has a chance to attack you.
Romulan collaborator V'Las managed to convince the Vulcan High Command to launch a preemptive strike on Andor in 2154. (ENT: "Awakening", "Kir'Shara")
Following Chancellor Gowron's demand that the Federation leave the Archanis sector, Jadzia Dax spoke to a friend in the Diplomatic Corps, who told her that several planets near the Klingon border were urging Starfleet to make a preemptive strike. (DS9: "Broken Link")