From Halopedia, the Halo wiki
Halo: Combat is a short video created in collaboration with Bungie Studios, Neill Blomkamp, Weta Digital and Origami Digital LLC. It is roughly 1:33 minutes long and is the second video in the trilogy, and was leaked on August 23, 2007. The video was officially released via WETA's website on August 28, 2007. On August 31, 2007, the video was revealed to be on the Xbox website under the name Combat: Part 1. The story told in the short was later concluded in Halo: Last One Standing.
The short film follows two UNSC Orbital Drop Shock Troopers fighting across a wasteland, being engaged by Covenant forces led by Brutes. The film starts off with two ODSTs of Alpha Team, Bravo-21 (T. Rymann) and Bravo-22 (S. Hartley), being tracked on an aerial camera as they move through a wasteland with gunfire going off around them along with several Banshee fuel rod strikes closely missing them.
Bravo-22 is tracking something on a hand-held scanner, and retrieves an elongated casing labeled "UNSC" from under a pile of debris while Bravo-21 gives him covering fire against fast-moving enemies. Superheated metal spikes impale the wall that they are near as a pair of Brute Minors open fire with Spike Rifles. Bravo-21 shoots them both with his BR55HB SR battle rifle, downing one as Bravo-22 calls for evacuation, prompting a D77H-TCI Pelican dropship to begin its descent to their position as Bravo-21 kills the second Brute with his battle rifle.
Bravo-21 is almost killed by a fuel rod cannon strike from a strafing Banshee. The Pelican drops off a M12 Light Reconnaissance Vehicle, prompting the ODSTs to make a run for it in the middle of an exposed area. Bravo-21 takes the driver's seat while Bravo-22 takes the passenger seat. Bravo-22 is then hit from an unknown source of fire, splattering smears of blood against the Warthog's windshield and the camera. The Warthog smashes through a wall then, shortly afterward, the film ends with 'Transmission Terminated, End Part 1'.
Open up on a black and white thermal live feed of two ODSTs running. Radio chatter can be heard in the background.
Cut to the two ODSTs running in parallel to a wall.
The ODSTs reach the end of the wall. They pause briefly.
The ODSTs move around the corner.
Cut to a shot of a group of Brutes advancing.
Cut back to the ODSTs who are still running. A fuel rod shot impacts a wall. Banshees fly overhead. The ODSTs come to another corner.
The other ODST, Bravo-21, takes up a defensive position, covering for Bravo-22. A single Brute runs by, not noticing him.
Cut to an overhead shot of Bravo-22 searching some nearby rubble. He eventually finds a large case. Bravo-22 picks up the case and moves back to join Bravo-21.
Brute Paegaas Workshop Spiker rounds suddenly whiz past the ODSTs, and embed themselves in the wall. Bravo-21 returns fire, killing one of the two attacking Brutes. The other Brute continues firing its Spiker.
Meanwhile Bravo-22 radios for assistance.
Pelican starts to descend.
Bravo-21 fires his weapon at the remaining Brute.
The Brute goes down. Seconds later, a Banshee swoops down and fires its fuel rod cannon. The bolt impacts nearby. The ODSTs are knocked off their feet.
The ODSTs get back up and return fire with their battle rifles.
The Pelican arrives and drops off its Warthog. Brute spiker rounds fired from offscreen hit a nearby wall.
The two ODSTs make a run for the Warthog. An overhead camera shot shows them entering the Warthog and driving off. The two Brutes they killed earlier are marked with orange indicator tags labeled "Threat Neutralized".
Cut to another camera vid (CAM 3) of the two ODSTs driving the Warthog. The names of the two ODSTs are displayed: T. Rymann (Bravo-21), and S. Hartley (Bravo-22).
Banshees fly overhead. A fuel rod shot impacts nearby. The Warthog is forced to make a sharp swerve.
A Brute spiker round hits Bravo-22. Blood splatters along the window.
Another Banshee flies overhead and fires a fuel rod shot. It misses.
Cut to Bravo-22's HUD. The warning message "INJURED" flashes in the upper right-hand corner.
The Warthog plows through a wall. Video feed from Bravo-22's helmet erupts into static.
TRANSMISSION TERMINATED. END PART 1.