From 1809 to 1981 Denmark was at war with Huéscar, bu 20 4, 1:56am

Same as Montenegro vs. Japan. (1904-2006)
Actualy, as Russian-Japanese war started, Montenegro also declared war, and few men joined the Russian forses. Russia lost the war 1905, but Montenegro didn't signed peace threaty, joined Kingdom of SHS (later Yugoslavia) and... forgot to sign it. Until 2006. when Montenegro declared independence.