The Resistance is an interstellar military union between several refugees of alien-destroyed civilizations. As of the War of 2016, humanity was elected as the leader of the Resistance.
According to the Sphere, the Harvesters and their Queens destroyed several civilizations by drilling into their home planet's molten core. The species which the Sphere is part of managed to hold them off for some time, but was ultimately defeated. Forced to retreat, the remnants of these annihilated civilizations united into one strong military union, the Resistance, which is currently engaged in war against the Harvester Empire.
War of 2016
In July 2016, the Sphere intercepted an alien distress signal which revealed their defeat on Earth. Seeing humanity's potential and attempting to save them from the impeding alien retaliation and evacuating them to the Resistance's world, the Sphere traveled to Earth to warn of the attack but was shot down by the Humans, who mistook it for an alien threat.
The Sphere was salvaged by the Earth Space Defense just as the Harvesters led by the IDR Queen attacked Earth. Although overwhelmed by the aliens, humanity managed to defeat the invaders by killing the Queen. The Sphere was humbled by the Humans's actions and, acknowledging them becoming the first alien-attacked world to successfully kill a Harvester Queen, chose them to lead the Resistance.