Earth-Yeerk War

The Earth-Yeerk War was a conflict between the human race and anti-Yeerk aliens and the Yeerks, parasitic aliens who sought to take over the planet. Being made aware of the planet after intercepting an old broadcast of Galaxy Quest, the Yeerks began an infiltration of Earth in the late 1960's. This initially proceeded slowly owing to the widespread proliferation of superheroes on Earth coupled with Yeerk worries about a nuclear exchange breaking out between the US and USSR with the Yeerks being caught in the crossfire. The Yeerks formed a front organisation known as the Sharing to lure people to become hosts. The Sharing was consciously modelled on groups like Keith Winton's Church of Practiology and Valentine Michael Smith's Church of All Worlds, both of whose groups were growing in this era. More religious elements were phased out after an attempted lawsuit by Lancaster Dodd, who accused the Sharing of deliberately modelling itself after his own group The Cause. The Yeerks feared this could draw unwanted attention and expose their infiltration too soon, especially as the Skrull invasion was a recent memory. Early Yeerk infiltration also had to contend with the supernatural, discovering how widespread it was on Earth after making the witch Dolores Umbridge a Controller. As this was all new to Yeerks, some argued it was not worth it to proceed with a large-scale takeover, though this faction ultimately lost out.

The Yeerks additionally squabbled over how thorough an invasion of Sol should be. The 10th planet Mondas was considered a target until the mechanization of the native population made it seem impractical. Back when the planet was known as Mongo, the population would have likely been suitable hosts to Yeerks but the Cybermen's mechanical forms offered them ample protection. The Yeerks would periodically raid Mondas to avoid the Cybermen becoming competition for Earth. The Mi-Go of Yuggoth and the Ganymedans were ultimately deemed unsuitable hosts, the Mi-Go in particular having driven Yeerks who infested them mad before rejecting them. An attempt to form a deal modelled on the one made with the Taxxons with the Vermicious Knids hit a snag when the Knids proved less reluctant with their ravenous hunger, which they quickly demonstrated to the Yeerk envoys who attempted to make a deal with them. The Yeerks retaliated with a bid to destroy all Knids, overseen by Vissser 2 whom was consequently absent from the invasion of Earth. However, there was a major debate in the Yeerk Council of 13 about trying to infiltrate Mars or the Moon. This debate was rendered moot by the Knids destruction of virtually all life on Mars and the Moon.

After the end of the Cold War, the Yeerks began drastically ramping up their infiltration, going from a few thousand controllers in 1990 to over 6 million worldwide by 1995. The Earth-Yeerk War's official beginning in 1996 is attributed to that being the year humans not under Yeerk control first took real notice of the invasion. A group of teenagers in Bahia Bay, California were the first to end up in this war after encountering the Andalite Prince Elfangir who gave them access to an Escafil Cube that let them gain the ability to morph into animals. While this team fought a largely secret war against them and dealt major blows to their operations, they were not the only ones to be aware of or combat the Yeerks. UNIT, the UN's alien defence body, would become aware of the Yeerks after a group of Controllers failed in a plot to place a Yeerk in the mind of Secretary-General John Wyrmwood. UNIT advocated a large-scale investigation to root out the Yeerks but were constrained by resource limitations. The presence of the Tiberium element and the rise of the Brotherhood of Nod from former Augment-aligned groups aiming to seize it meant the UN was fixated on the Global Defense Initiative. The Exalt and their allies in the Syndicate likewise became aware of the Yeerks in 1997. The Exalt ordered their Syndicate allies to prevent the schismatic Men in Black faction as well as other groups like the SCP Foundation and Torchwood Institute from finding out about the invasion. While the Exalt did not truly want a Yeerk-ruled Earth as it was antithetical to their own agenda, they saw an opportunity to soften the Earth up for their planned 2012 conquest by helping the invasion grow. Stargate Command was made aware of the Yeerks in 1997, but owing to limited intelligence presumed they were simply a faction of Goa'uld and thus only had limited engagement against them prior to 1999.

While the Yeerk infiltration was global, the Yeerks prioritized securing California as their main fiefdom. By 1997, virtually every major town in California had a Yeerk presence. Sunnydale was the largest exception, as that town's mayor Richard Wilkins had, after an attempt to forcibly make him a host at a meeting with leaders of The Sharing, absorbed the Yeerk in his head and threatened to unleash demonic forces on the invaders if they set foot in his fiefdom. In a bid to draw American security operatives to the state, the Yeerks made the leadership of the white nationalist group the Order into Controllers, who then stoked Earl Turner's attempt to trigger 'the Day of the Rope' as part of a gambit to make FBI and military personnel into Controllers. This scheme would ultimately largely be unsuccessful. An attempt to infest the G8 leadership (Josiah Bartlet, Adam Lang, Sergei Karpov, Hayato Igashari, Clark MacDonald, Martin Schormann, Grace Bellanger and Marco Abiatti) during a conference in San Diego was foiled by the aforementioned teenage team. The war with the Yeerks remained a low-level guerrilla affair until the Yeerks attempted to make California Governor Eleanor Watson into a Controller after infesting her second husband (whom she had married shortly after he saved her from an assassination plot headed by her first husband Brendan Grant). Governor Watson was saved from the Yeerks and publicly revealed them to the world in 1999.

With their exposure, the war with the Yeerks became public. The Yeerks destroyed Bahia Bay, though many were able to escape the city. Open conflict with UNIT and the US military took place across the globe. UN space assets discovered the Yeerks were dispatching a large space force to reinforce the Yeerk pool ship in orbit, with a secondary goal of crushing human defences. With an Andalite presence at the time lacking, a human-led space fleet was formed. The flagship was the vessel the Archangel Michael, the ship that had brought humanity victory over the Fithp. That race, ironically, also was a participant in this fleet. The Chtaptisk Fithp herd viewed its loyalty as now belonging to the 'herd' who had defeated them which they viewed as the United States. Rounding out the force was a collection of reprogrammed Harvester spacecraft, an orbital weapons platform created by Tony Stark and several superheroes led by Captain Future. While the Yeerks had a technological advantage, they were taken by surprise by this force which bought enough time for support from the Coalition of Planets (an ally of the Andalites formed originally to resist the Viltrumites) to wipe out the remaining Yeerk fleet and the Pool Ship was denied crucial reinforcement as it was targeted from the Earth. The Yeerk defeat was triggered shortly after when Jake Berenson, the leader of the guerrilla fighters on Earth, blew a hole in the ship that sucked an estimated 150,000 Yeerks into the vacuum of space. This act, while a war crime, did force the Yeerk forces to surrender. Esplin 9466, the Yeerk leader who held the title of Visser One, was captured and tried for war crimes in The Hague. Remaining Yeerks were forced to leave human hosts and the planet as well.

The war produced a number of consequences for humanity. The Hork-Bajir and Taxxon aliens used as hosts for the Yeerks remained largely on Earth, the latter using the Andalite Escafil Cube to morph into less ravenous life forms. The UN declared reservations for the Hork-Bajir in Jellystone National Park and the Taxxon nothlits in the Amazon. Both species' presence would help fuel human supremacist sentiment. The Hork-Bajir joined the Tectonese as a common punching bag for the American far right. Senators Bob Roberts and Kevin Keeley would for the remainder of their respective careers introduce bills calling for the Hork-Bajir settlement to be dissolved. Andalite advocacy and relations with them helped stave off the mainlining of this prior to 2009, when contact with them was lost. The cause of the Andalites' disappearance remains unclear, with rumours including Dalek attack, devouring of the planet by Galactus, Viltrumite conquest or something more local. The Escafil Cube technology was shared with the human race by the Andalites and used for both military and civilian purposes (including largely replacing hormone replacement therapy for transgender people) but after the loss of the Andalite homeworld, the Syndicate seized all of the Cubes present on Earth into their custody and it is believed the Exalt had them destroyed.