There are several claims of wars extended by diplomatic irregularity, often by a small country named in a declaration of war being accidentally omitted from the concluding peace treaty of a wider conflict. These alleged extended wars have only been "discovered" after the fact, and had no impact during the long period (often hundreds of years) they were supposedly de jure in force.
The "discovery" of an extended war is often an opportunity for a ceremonial peace to be contracted by local authorities.
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, or there being no formal peace treaty at the end of the Korean War (though it is worth noting that in October 2007, North Korea and South Korea agreed to seek a peace treaty[1]).
| Combatants | Historical conflict | Declaration of war | De facto peace | Ceremonial peace | Status of claim |
|---|---|---|---|---|---|
| Delian League vs Peloponnesian League | Peloponnesian War | 431 BC | 404 BC | 1994 | Although Athens and Sparta were allied in later conflicts no peace treaty was ever signed |
| Roman Republic vs Carthage | Third Punic War | 149 BC | 146 BC | 1985[2] | There was a contract of surrender between the Roman and the Carthaginian commander. |
| San Marino vs Sweden | Thirty Years' War | 1614 | 1648 | Spurious reported date: 1996[3] |
San Marino was never party to the war.[4] |
| Isles of Scilly vs Dutch Republic | English Civil War | 1651 | 1651 | 1986 | Not clear that war was actually declared on Scilly, rather than its rebels. |
| Berwick-upon-Tweed vs Russian Empire | Crimean War | 1853 | 1856 | 1966 | All legal references to "England" applied equally to Berwick by this time. |
| Principality of Montenegro vs Empire of Japan | Russo-Japanese War | 1904 | 1905 | 2006[5] | Montenegro declared war in support of Russia but this was merely a gesture as Montenegro lacked a navy or any other means to engage Japan. |
| Andorra vs German Empire | World War I | 1914 | 1918 | 1958[6] | Andorra was not invited to the Treaty of Versailles. |
| Costa Rica vs German Empire | World War I | 1918 | 1918 | 1945[7] | Due to a dispute over the legitimacy of the government of Federico Tinoco Granados, Costa Rica was not a party to the Treaty of Versailles. The technical state of war would have ended with Costa Rica signing a peace treaty with Germany after World War II. |
| Allies of World War II vs Nazi Germany | World War II | 1939 | 1945 | 1990[8] | At the time World War II was declared over, there was no single German state that all occupying powers accepted as being the sole representative of the former Reich. Therefore the war technically did not finish until the country was reunified. |
| U.S.A vs Germany | World War II | 1941 | 1951 | 1990[9] | It was not until the Treaty on the Final Settlement with Respect to Germany signed in 1990 that peace was formally established. However, in 1949 some technicalities were modified in to soften the state of war between the U.S. and Germany. The state of war was retained since it provided the U.S. with a legal basis for keeping troops in Western Germany[1]. As a legal substitute for a peace treaty[2] the U.S. formally ended the state of war between the U.S. and Germany on October 19, 1951 at 5:45 p.m. According to the U.S. a formal peace treaty had been stalled by the Soviet Union[3] |