The trailer confirms what Halo: Reach's title hinted at: The game will depict some of the same events that took place in the novel Halo: The Fall of Reach by Eric Nylund. The book portrays both the siege of the titular fortress planet by the Covenant and the origins of the Spartan program, which developed dozens of super-soldiers like Halo series hero Master Chief.
While the siege of Reach was briefly shown in the E3 teaser trailer, it is confirmed in the new video spot by a radio message saying "Winter Contingency has been declared." The same line appears in Fall of Reach when the Covenant began a full assault on the planet, smashing its defenses and landing thousands of dropships on its surface.
The new Halo Reach trailer also shows multiple Spartan soldiers. According to Microsoft, the six-Spartan group is Noble Squad, the military unit which will be the focus of Halo: Reach. The game will chronicle their battles with the Covenant as they try and protect Reach's human inhabitants from their relentless onslaught.
Speaking with GameSpot, a source who has seen Halo: Reach first-hand describes it as "Gears of War with Spartans" and "very bleak and violent." The trailer hints that the game will be grimmer in tone than previous games, with all members of Nobel squad bearing facial scars and one sporting an artificial arm. Another bears a Gears-like skull on the front of his helmet and wields a kukri-like curved machete, hinting at bloody bladed melee combat.