The final argument of kings. Louis XIV of France, recognized that force is the final argument, so he directed that his cannons carry the engraving "ultima ratio regum" (1650). As a result, this phrase usually signifies "war" or "the use of military weapons; force". The phrase was adopted in the form of "Ultima ratio regis" for the same purpose which appears on cannon cast for Frederick the Great, king of Prussia, c. 1742.