Dawn of War

Dawn of War is a real-time strategy game in which you play as The Space Marines Chapter, the Blood Ravens. In mission 4, Destroy the Xenos, the Blood Ravens are deployed to destroy an Ork Waaagh! that has gathered on Taturus. The Orks are being, unknowingly supplied to the Blood Ravens, by the Chaos Space Marines.

http://www.youtube.com/watch?v=UID6LEzvRRo