Halo 2
The game is set in the same fictional world as the rest of the Halo series. Much of the game takes place in the future year 2552, over 500 years from now. In the story line humans have developed faster than light travel, and now live on many planets  and moons of the Solar System. On humanity's first try to build a settlement on a planet around another star they met the alien Covenant. The Covenant declared religious war on humanity. At the start of Halo 2 humans are losing the war and the Covenant have just discovered Earth.