Army of the Ages
One of the standard uses of Time Travel for an Evil Overlord is to pluck warriors from various wars throughout history and bring them through to the future (the Evil Overlord's present) and assemble them into an unbeatable army. The low manpower of pre-Agricultural Revolution armies compared to modern ones will always be ignored
Occasionally, more heroic entities will use this as a means of recruiting a Time Police force.
When an army is made up solely of recognised historical figures, that's an Archived Army. And if a group of dead people are brought together to pass judgement on the living, that's a Jury of the Damned.
- The Fourth Ninja War arc of Naruto features heavy use of a resurrection jutsu that brings back a wide range of ninja that had been previously killed. Everything from past villains the protagonists had faced to legendary ninja who had been dead for decades.
- In Mahou Sensei Negima, Lifemaker summons all previous generations af Cosmo Entelechia upon his/her resurrection.
- Reinhold Borsten did this in the Hex comic book series. This is how gunslinger Jonah Hex got transported to 2050.
- The 2008 DC Comics mini-series The War That Time Forgot centered on this, with various characters from DC's war books dragged through time and dropped on Dinosaur Island. (The series is in fact named after one of the features from one of those comics that took place on Dinosaur Island.)
- Inverted in X-Men, where Fitzroy tries to conquer the present (his past) with future sentinel technology. It finally backfires spectacularly when he opens a portal to a prison riot in the future, bringing in a horde of mutant inmates — Bishop follows.
- The Avengers's foe Kang once had his own team of elite warriors plucked from different time periods, The Anachronauts.
- Kang and his counterparts have also employed the Legion of the Unliving, made up of time-plucked characters who are thought dead in the present.
- A notable example is during Avengers Forver were Kang allies with the Avengers to fight a Army of the Ages sent by his older self Immortus.
- This is the setting for Fritz Leiber's Change War stories, but the stories are all told by grunts who have no understanding of the big picture.
- Neal Asher's book Cowl features a Roman Legionnaire, an assassin from a cyberpunk future and a Neanderthal on the same team.
- The Tamuli has the bad guys doing this. But it's less effective than most examples as the Army of the Ages are usually bronze age soldiers who are up against knights in full plate.
- Edward Eager's Knight's Castle has a variation: the protagonists, four children, have been shrunk to a tiny size and the world of their toy knight figurines has come alive. They win the day in the end by bringing in one child's collection of toy soldiers, which includes soldiers from several different historical wars.
- Nearly any military force in the Riverworld books is this trope, by nature of the series.
- Percy Jackson and The Olympians has an example, but it isn't time-travel related. The fortress of the Greek god Hades is guarded by dead soldiers from all of history: Skeletal Roman legionnaires with spears are joined by undead US Marines with assault rifles.
- The Star Trek TOS novel Time for Yesterday by A.C. Crispin had a scene in which Spock's son Zar (long story) and Kirk pulled Spock's leg by suggesting they use the Guardian of Forever to recruit a number of military leaders who could "advise" Zar's army 5000 years in the past. Alexander the Great, King Arthur (referred to as Artos), Julius Caesar, Geronimo, Genghis Khan, a general named Voltag from pre-Surak Vulcan ... they considered Patton, but decided he was too modern for the Tech Level the army used.
- A variation not involving time travel occurs in Keith Laumer's A Plague of Demons: extraterrestrials have been harvesting the brains of soldiers from Earth's wars and using them for Man in the Machine super-tanks. This has gone on for centuries....
- The Bangsian Fantasy Legions of Hell by C. J. Cherryh invokes this. Some of the souls in Hell have joined forces with others from vastly different periods, and if they have enough mental flexibility, they can use weapons and tools from times long after their deaths. This leads to Gaius Julius Caesar riding in a jeep and carrying an Israeli-made assault rifle, Achilles piloting a black helicopter with loads of CIA spy gear, Hatshepsut riding in Marc Antony's red Ferrari convertible (driven by Kleopatra) ... while the Viet Cong attack, apparently on orders from the king of Assyria....
- The War Lord does this in the Doctor Who serial "The War Games".
- In the episode "A Good Man Goes to War", The Doctor himself does this. He recruits the space-spitfires from Churchill's England, space pirates, a Sontaran nurse, a lesbian Victorian detective Silurian, her girlfriend Jenny, and an entire army of Silurians. Word of God says that he wanted the immortal Captain Jack Harkness by his side as well, but the actor was busy making Torchwood: Miracle Day.
- Star Trek: Voyager does a scaled down version of this when the ship is broken into multiple time frames. In order to remove Seska and the Kazon from engineering (it being the time they took over the ship in that section), Chakotay recruits Icheb and Naomi from the future, Torres and some Maquis from the day they arrived in the Delta Quadrant, Janeway and Kim from before the mission began, Paris from the relative present, and finally the still-Borg Seven of Nine.
- Eternity's Rangers from GURPS: Time Travel.
- The basic premise of the Magic: The Gathering CCG, with you as the summoner.
- The SPI board game Time Tripper allowed you to play a Time Tripper, who went forward and backward in time to recruit soldiers as allies.
- In Scion, the Einherjar warriors that show up in modern times come from the 18th century through the mid-1970s, outfitted in whatever gear they had on them when they "died".
- This is the plot of the recent first-person shooter Darkest of Days. Well, the organization that recruits you out of the American Civil War apparently isn't evil, and is more of a Time Police. But they still do most of their recruitment by plucking skilled soldiers out of various wars throughout history, namely people who were considered 'missing in action' anyway.
- The Fallout 3 expansion "Mothership Zeta" has you team up with several cryogenically-preserved warriors on the alien spaceship: a military doctor from Operation Anchorage, a contemporary slaver, a wild west cowboy, and a samurai. And a little girl from during the Great War.
- You also would've had an astronaut, but he didn't survive the thawing process.
- Common in many Hanna-Barbera cartoons. Standard villainous armies tend to include Goths, Mongols, Vandals, and the like.
- High Priest: Yes! With stones of varying sizes! The rocks represent the pinnacle of Modern Warfare! And so long as our rocks are heavier and our sticks pointier, the Gods will favor us! (...) Behold! More gifts from the heavens!