The Four Years War was a conflict that took place between the United Federation of Planets and the Klingon Empire in the mid-23rd century. (FASA RPG: The Four Years War)
After the war ended, the political movement Quattuor Anni (Latin for "Four Years") arose. Among its numbers were Starfleet veterans and families of casualties of the Four Years War. (More Missions, More Myths 18: "Fatal Vision")
The Four Years War took place from 2255 to 2259. Among the noted commanders of the war were Captain Garth of the USS Constitution and Captain Robert Wesley of the USS Avenger.
Noted battles of this war included the Battle of Omicron Canaris.
In this continuity, the four years war occurred between 2247 and 2250. Three of the most notable Captains were Samuel Trask, Sonya Alexander, and Kelvar Garth of the USS Ares.