Hub:Halo 3/Story
From Halopedia, the Halo wiki
Halo 3 is set in the final months of the year 2552 and several hours after the end of Halo 2. Following the Covenant invasion of Earth and the eruption of the Covenant civil war, the High Prophet of Truth and the remainder of his loyal forces have descended upon Earth. John-117, stowed away with the Covenant, has come to finish the fight while these forces begin digging something up in the East African savanna.