Spartan 1.1 faction
From Halopedia, the Halo wiki
This faction is a vigilante group of thirteen Spartan 1.1s who banded together on Earth to take the fight to the Covenant. According to Kevin Morales, who later admitted to Janissary James that he was exaggerating slightly, they own a 100-meter yacht upgraded with everything an ONI spy ship would have.
In case the Covenant attacked first, as they ended up doing, they made suitable arrangements on Earth. These included having bunkers on each continent, three Pelicans (one in Switzerland, one in Chile, and one in Mongolia), Warthogs within three kilometers of 15 major shuttle ports, a stash of weapons on a rooftop in Old Mombasa, and more.