Fort Acorn was an Acorn Army stronghold located just outside of Robotropolis. It was created after the city had been destroyed by a Station Square nuclear strike in order to protect the dome shield which contained the harmful radiation from the nukes. The Fort contained the Mes Braves Battalion, which was commanded by the infamous general Armand D'Coolette. Fort Acorn became a battle ground following Sonic the Hedgehog's return from a year in outer space, as Dr. Eggman launched an armada of SWATbots to bring down the dome shield, in order to allow the radiation to spread. His SWATbot horde was ultimately destroyed however by the combined might of the Mes Braves Battalion, the Chaotix, G.U.N. agents and Amy Rose.