There are different claims of wars extended by diplomatic irregularity, sometimes by a small country named in a declaration of war being accidentally omitted from a peace treaty concerning the wider conflict. These "extended wars" have only been discovered after the fact, and have no impact during the long period (often hundreds of years) after the actual fighting ended.
The discovery of an "extended war" is sometimes an opportunity for a ceremonial peace to be contracted by the "belligerent parties".
Such a situation is to be distinguished from that of parties deliberately avoiding a peace treaty when political disputes outlive military conflict, as in the Kuril Islands dispute between Japan and Russia. In the case of the Korean War, the fighting formally ended when an Armistice Agreement was signed in 1953, but there has been no formal peace treaty between the Koreas (though in October 2007, North Korea and South Korea agreed to seek a peace treaty.)