Star Wars: Rogue One Trailer 2 - 14 Major Plot Clues
4. Protectors Of The People
This trailer seems to set up the idea of Chirrut Îmwe and in particular Baze Malbus as the protectors of the Empire's victims.
Baze specifically mentions the fact that the Empire destroyed his home and that he now fights them. It's almost as if he and Chirrut (who seems more focused on protecting the Holy Land of Jedha) are on a mission of revenge.
Unfortunately, that sort of personal, emotional agenda is exactly the kind of thing that gets people killed on missions like this...