Still Fighting the Civil War

Some people just can't let go of the past, but this guy really takes it to extremes. It's not even his past, but he's still bitter about real or perceived injustices that happened before he was born, and will let anyone in earshot know, given half a chance.

The stereotypical version is someone from the Deep South who's always complaining bitterly about "The War of Northern Aggression", but it can also apply to plenty of other conflicts, real or fictitious.

Very much Truth in Television. This is similar to, but different from, The Remnant, where a character is literally still fighting against his enemies from a war that he actually took part in, but which is now over. See also Mexico Called They Want Texas Back.

Literature

 * MacIan in The Ball and the Cross by GK Chesterton fervently supports the Jacobite cause, a century and a half after their last attempt to claim the throne was defeated.

Live Action TV

 * Borderline example: Mal in Firefly. He actually did fight in the war with the Alliance, but his attitude during the show is mostly restricted to grumbling and griping, not trying to continue fighting for a lost cause.
 * His backstory has him continue fighting the final battle battle of the civil war, the battle of Serenity Valley, leading thousands of other Independent soldiers even after their top superiors had surrendered and officially lost the war.
 * The comics include a terrorist group of former Independent soldiers who have vowed never to stop fighting the war against the Alliance.
 * The Peacock family from the infamous The X Files episode "Home." When Mulder & Scully come across the matriarch, she rails at them about the War of Northern Agression.
 * In Jack of All Trades, Jack runs into his friends Lewis and Clark, famous explorers with horrible sense of direction, who has yet to be informed that the war with Britain has ended. When they encounter Emilia (Jack's british partner) they capture her, and refuse to believe Jack's claims of her being on his side.

Western Animation

 * On one Looney Tunes short, Bugs Bunny encounters a Rebel general (Yosemite Sam) who still believes the war is on. When Bugs informs him that the war ended almost a century ago, Sam's response is "I ain't no clockwatcher!"
 * The Rocky and Bullwinkle episode "Wossamotta's Shining Season" is all about this trope. Bullwinkle and Rocky play football, and at one point the whole thing turns into a reenactment of a Civil War battle. There's a southern, Kentucky-colonel-type character who can't abide the use of the word "Civil" directing things, and a character actually says, "Shoot, they're gonna fight the whole war over again!" (But this time, the "Sooth" wins)
 * In a Deputy Dawg short, the gang encounter an old Confederate soldier causing trouble who thinks the war is still going on.
 * Commander Clash falls into this for part of his first episode of Captain Planet and The Planeteers.

Real Life

 * Real Life example: Among Argentines, This attitude towards Las Malvinas is so common that it borders on Hat status for the entire nation.