The action ramps up in episode 4 of Halo 4: Forward Unto Dawn.
Halo 4: Spartan Ops Extended Behind the Scenes
343 Industries and Axis Animation talk about creating the unprecedented Spartan Ops content for Halo 4.
Making Halo 4 - Part 1 and 2
Join 343 Industries on a 20 minute behind the scenes featurette on the creation of Halo 4.
Halo 4 - Concept Art Trailer
There is some inspiring scenery in this concept art trailer for Halo 4 from 343 Industries.