Sierra 117

Landfall is believed to be the first campaign mission of Halo 3.

It takes place in a jungle.

According to the Halo 3 E3 2007 Trailer, it begins with three Pelican Dropships descending from an orbiting Covenant warship, evading enemy warships in orbit, and then carrying SPARTAN-117 and a group of Marines, possibly including Avery J. Johnson, onto the Earth's surface. This is where it is believed that the Chief and the Arbiter first meet and join forces.

Upon completing it on the Normal, Heroic, or Legendary difficulties, the player will earn the "Landfall" achievement and 20 Gamerpoints.