These trailers show gameplay, weapons and the story. It also tells us that it will be cross platform via cloud saves. The new screenshots and trailers were released as an official press release from Microsoft.
Xbox user Mighty Link posted on the Xbox forums that playing Halo 4 has triggered a trailer for Halo: Spartan Assault, He has no idea why or how. He quickly grabbed his mobile and took some screen shots, which you can find below.
As you can see, it shows that it’s a mobile game. Its possible that the game will link to the Xbox One and mobile and allow cross platform gaming.
We’re treating this as a rumour for now. But we’ve reached out to Microsoft for an official statement.