----- X-COM ----- The Extraterrestrial Combat Unit (or X-COM) was formed to combat the increasing world-wide UFO activity at the end of the 20th century, X-COM is an independent body charged with investigating and defeating the alien threat. This elite multi-national organisation is funded by all the major world powers and is equipped with the finest pilots, soldiers, scientists and engineers. ---------- Background ---------- Earth 2039. The last scarred sites of the alien war of 30 years ago are healing (as featured in X-COM: Enemy Unknown). To all intents and purposes the threat to the Earth may never have happened. But in the oceans long-silent forces have been aroused by the conflicts; a vast interstellar colonisation ship - 400 billion tonnes of metal - that fell to Earth 65 million years ago has been activated. When the alien base on Mars shuddered in its death throes a powerful Tachyon beam darted out to a long dormant receptor. 30 years ago, the vast chambers of unnumerable species began their re-animation cycle. X-COM must now face a new terror: an army of aliens already installed in the depths of the world's oceans. The aliens have been sinking ships, destroying planes and devastating remote ports, to what end we know not.
Official Timeline (from X-COM Interceptor Manual)
---------------------------- The Second Alien War (AW-II) ---------------------------- 2041 ---- January 1st: The Second Alien War begins, Sightings of the alien submersible vehicles increase dramatically as the aliens become more bold. Once again, one of the main goals of the alien forces is to terrorize the population of major metropolitan areas. This time around, the aliens stick to regions near the world's oceans. Although some species, the Aquatoids in particular, are obviously related to the last wave of aliens who attacked the planet, many of these creatures are different than anything previously encountered. Although interception of the smaller alien subs is a relatively easy matter thanks to the Barracuda intercept sub, early X-COM tactical missions meet with less than successful results. Most of the weapons used in the First Alien War are useless without a supply of Elerium-115 to power them, and weapons based on Earth technology, such as the Laser Rifle, prove to have no effect against the new aliens or cannot be adapted for underwater use. Aquanauts are forced to rely on primitive spear and harpoon gun, torpedo launchers, and a small array of explosive devices, until they are able to research the technology used by the new wave of alien invaders. --------- 2042-2045 --------- The Second Alien War ramps up to a fever pitch. More alien species are catalogued. One species in particular, a clawed group of creatures that quickly become known as "Lobster Men", cause Aquanauts a great deal of difficulty. Their tough skin is virtually impervious to conventional methods of attack. One of the earliest alien technologies discovered is Zrbite, a mineral analogous to Elerium- 115 and used to power most of the new aliens' equipment and weapons. Zrbite is found to be extremely unstable, but its use is deemed a necessary risk; it is the only viable power source for replicated alien technology. The influx of equipment and aliens, dead and otherwise, recovered from the battlefield leads to great advances in weapons technology. Primary among these are the ability to replicate sonic weapons and the development of Vibro Blades - rotating titanium blade weapons that prove quite effective against the deadly Lobster Men. Along with weapons technology, X-COM scientists discover new methods of construction personal armour, which provides aquanauts the protection they need in extended battles. ---- 2046 ---- After just over five years of constant fighting, X-COM scientists discover the location of the aliens' hidden base: T'leth, a huge alien colony ship that lies at the bottom of the Sigsbee Deep in the Gulf of Mexico. Travelling aboard a new Leviathan submarine, the only armed submersible craft capable of withstanding the pressure at these great depths, a squadron of aquanauts descend upon the alien stronghold. After a fierce battle, the aquanauts locate the reanimation chamber of the alien controlling force; a huge, tentacled being known only as the "Alien Horror". Luckily, the X-COM force arrives before the reanimation process is complete. In destroying the power nodes of the lead alien's cryogenic coffin, the aquanauts set off a chain reaction that destroys the alien colony ship just as it is rising above the surface of the water. All the aquanauts aboard are killed, but in dying they ensure the safety of the people of Earth. After the destruction of T'leth, the remaining aliens prove no problem to eradicate. The Second Alien War is officially declared over January 19, 2046. -------- END FILE --------
And the timeline continues through Recovery and Progress.