The player takes on the role of Mobius 1, an elite fighter pilot serving in the Independent States Allied Forces' (ISAF) air arm, fighting against the Eruseans who have occupied almost all of the Usea continent after an apocalyptic event in 1999. A massive asteroid, codenamed Ulysses 1994 XF-04, struck Usea, killing 500,000 people and turning many into refugees. Erusea used this as an opportunity to occupy the continent after a prolonged military buildup. They achieve military supremacy via the superweapon Stonehenge, a megastructure battery of railguns that were originally designed to destroy asteroids but have been found to be effective against airplanes as well. This allows Erusea to dominate much of the airspace over the continent giving their military a powerful strategic advantage. Consequently, ISAF has been pushed back to the eastern coast of Usea.