On July 2, 1996, Earth was invaded by an alien species called the Harvesters who were seeking to harvest planet Earth's natural resources at the cost of wiping out human life. Within 48 hours, one-hundred-and-eight human cities were destroyed. On July 4, humanity managed to strike back at the invaders when MIT graduate and environmentalist David Levinson managed to implement a computer virus into the aliens' mothership and disrupting their force-field technology. The mothership was destroyed with a nuclear device thanks to the efforts of Levinson and USMC Captain Steven Hiller, and the remaining aliens are neutralized.
In the aftermath of the invasion, humanity recovered and becomes more politically united against a common threat that almost saw their extinction. In response to possible future extraterrestrial threats, the United Nations created the Earth Space Defense. Within a span of twenty years, humanity has a unprecedented era of peace without a major war or genocide or police action.
On July 3, 2016, the ESD lost contact with Rhea Base and learned that it was destroyed immediatly after an immense wormhole had been created there. Then, ESD soon lost contact with their base on Mars caused by the same aliens of the 1996 invasion.
On July 4, during the 20th anniversary celebrations, the aliens arrived in full force in the form of a 3,000 miles massive "Harvester" mothership. The sudden arrival of the Harvester caught Earth forces off guard as it quickly destroyed the Moon base and Earth's orbital defense before making landfall for the planet.
The Harvester lands over the North Atlantic Ocean and causing the lifted structures and debris to rained over Europe, and its landing annihilates the entire United States East Coast and much of northwestern Europe.
ESD Director David Levinson was on the Moon investigating the wreckage of the unknown ship and recover a container. After being literally swept up by the arrival of the Harvester, Levinson and his companions took the container to Area 51 and opened it to reveal a giant white sphere of artificial intelligence. The Sphere explained to the humans that is was sent by a party of refugees within the Resistance to help evacuate humanity to a refuge planet occupied by a resistance force of countless other races which opposed the harvester aliens.
Desperated, Levinson and Dr. Brackish Okun organize an alternate plan to kill the Alien Queen. Realizing that the aliens are invested in finding the Sphere and that the Queen is locked on to the Sphere's "RF frequency", Levinson and Okun put the Sphere in an isolation chamber and duplicate its frequency into a transmitter on a space tug to lure the Queen into a trap filled with a cold fusion bomb.
After the frequency is activated, the Queen and her forces were lured into the trap. During the subsequent battle, Whitmore leads the Queen's warship to the trap as the space tug is taken to the warship. The Queen soon realizes that it is a trap, but it was too late to escape as the warship is trapped in a force-field and Whitmore detonates the bomb. However, the Queen barely survives by using a personal force-field on her exoskeleton.
After bypassing Area 51's defenses, the Queen almost obtains the Sphere until Patricia Whitmore commandeered a fighter and destroys her shields projector, allowing Captain Hiller and his surviving squadron, who hijacked alien attackers, to finally kill the Queen. With the Queen dead, alien forces were in disarray. The Harvester stops its excavation and retreats into space.
Impressed by human courage and strategy, the Sphere offers humanity the leadership of the Resistance, which accepts. After the war ended, humanity's technological advancement was boosted by millenia, with interstellar faster-than-light travel being achieved by manipulation of wormholes.