Earth is the third planet in the Solar System. It is a terrestrial (rocky) planet, both the densest planet in the system and the largest of the system's four terrestrial planets. Earth is the homeworld of humankind. The planet has one Moon.
On July 2, 1996, Earth was invaded by an alien species called the Harvesters who were seeking to harvest the planet's natural resources at the cost of wiping out all life on the planet. Within 48 hours, one-hundred-and-eight human cities were destroyed. On July 4, human military forces mounted a successful counteroffensive against 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 were neutralized.
In the aftermath of the invasion, humanity recovered and Earth's nations were 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 and reverse-engineered Harvester technology to enhance their technology for military, aerospace, and civilian use. Within a span of twenty years, humanity had an unprecedented era of peace without armed conflicts, genocide, or police action.
On July 4, 2016, on the twentieth anniversary of the War of 1996, Earth was again attacked by the Harvesters. Despite the efforts of the ESD and Earth's planetary defenses, the aliens' massive mothership destroyed Earth's defenses, devastating parts of Europe, Asia, and the American eastern seaboard. The mothership landed over the North Atlantic Ocean and attempted to harvest the Earth's molten core that would have destroy the planet in the process.
During this time, humanity came into contact with an benevolent alien virtual intelligence dubbed the "Sphere" which explained its failed attempt to evacuate Earth's inhabitants and its intentions to unite multiple alien races opposing against the Harvesters. In a final act of desperation, the ESD organized a trap—by using the Sphere's presence—to lure and kill the Harvester's Queen out from her ship. The trap partly succeeded, leading to the alien forces falling into disarray and the mothership retreating from Earth.