Blue Six

Blue six is the unit present in the very start of the Halo Wars Announcement Trailer, they were shown to be in an outfit of 4 M12 LRV Warthogs and two modified (turretless) Warthogs. The outfit is seen leaping over a rise in a snowy night landscape (the exact planet is unknown) and after that showing 2 marines from the outfit radioing in to the UNSC Spirit of Fire to confirm their joining with Blue 5'' (which is another outfit consisting of 5 M808B Scorpion tanks). Both units are finally shown heading towards the last-known position of a recon force whom communications were severed. It is unknown what happens to Blue 6 and their fate after that scene. =Sources=
 * 1) Halo Wars trailer.