Twilight: 2000

Tabletop Games set in the aftermath of World War Three (which took place in the late 1990s in that universe) and popular during the 1980s. Still played today, though- RPOL has a number of games in the setting.

Suffered massively from The Great Politics Mess-Up, rapidly becoming redundant with the end of the Cold War. The second edition featured a new timeline, which didn't prove popular. Especially in Germany, since whereas NATO launching a land invasion of Poland made some kind of sense when the latter was part of Commie Land, the new timeline basically had Germany starting WWIII by invading Poland. This led some players to disregard it and use the original timeline, treating the whole thing as an exercise in Alternate History.

A science-fiction RPG from the same publishers advanced the first-edition timeline three hundred years and moved the action into Earth-colonized space. Originally called Traveller: 2300, the name was soon changed to 2300 AD since it had nothing to do with any flavor of the Traveller RPG. 2300 AD featured Cyberpunk influences, a war with aliens who were biologically obligated to be a Warrior Race, and the French domination of Earth and interstellar politics.

MERC 2000 was a version that used the basic rules in a modern setting. With mercenaries.

A reboot, Twilight 2013 was released in late 2009.

The first scenarios were set in Poland, which surprised some of the Polish roleplayers, and they featured horribly mangled Gratuitous Polish.

Not be confused with Twilight, with which it probably doesn't have a large crossover demographic. Though a crossover fic between the two would be hilarious, confusing the two is one of the Things Mr. Welch Is No Longer Allowed to Do In An RPG.

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Provides examples of:

 * After the End: Kind of the point of the game.
 * Army of Thieves and Whores: Many military units have turned to banditry and pillage in Europe.
 * Divided States of America: The prewar United States government has actually split into 'Civgov' (the old civilian federal government apparatus, led by Congress, the Supreme Court, and the President) and 'Milgov' (the United States military ruling its territory as a totalitarian dictatorship, led by the Joint Chiefs of Staff). Confusingly, Civgov has its own military consisting of units which have defected from Milgov and units mustered after the end of the war, meaning that for the duration of the setting there are actually two Armies, two Navies, etc. Taken together, the two control about a quarter of the old United States, with the rest ruled by a wide variety of different tribal warlords, local powers, foreign invaders, and the neo-Nazi 'New America' movement.
 * Fallen States of America: Several of the sourcebooks, written as historical texts on past events, reveal that this is what eventually happens to the United States after the time in which the setting takes place. The nuclear autumn combined with the ongoing civil war results in a nation that doesn't have enough arable cropland to feed its population, in addition to all the other problems that come with the apocalypse. The different factions are eventually forced to call off the civil war and peacefully reintegrate in a desperate effort to save what little remains of the country.
 * Hopeless War: Nothing has really been solved by the war. The setting is more about survival and going home than accomplishing any of the war's original objectives.
 * Modern Battlefield Weapons: Modern at the time, anyway. Some of the slightly more futuristic stuff, like the German army issuing the G11 as a standard weapon, never happened in reality.
 * Trapped Behind Enemy Lines: The introductory adventure features this for the players.
 * Urban Warfare: This happens quite often in the game, though the biggest cities are usually radioactive craters.
 * War Is Hell: Amen.
 * World War III: A limited nuclear exchange with a lot of conventional ground fighting mixed in.