It could also be based loosly on world of warcraft. And damn that trailer is epic i cant wait. Also i hope that music from the trailer will ceature througout the movie. According to whats below i would suggest its before thrall
The film portrays the initial encounters between the humans and the orcs and takes place in a variety of locations established in the video game series
Azeroth stands on the brink of war as its civilization, led by the humans, faces a fearsome race of invaders: orc warriors fleeing their dying world of Draenor to find their place in another. As a gateway known as the Dark Portal opens to connect the two worlds, the humans face destruction while the orcs face extinction. Anduin Lothar (Travis Fimmel), leader of the humans, and Durotan (Toby Kebbell), leader of the orcs, are then sent on a collision course that will decide the fate of their families, their people and their home.