Shia LaBeouf was originally cast, but had to drop out. Charlie Hunnam was then cast, but then was later replaced by Casey Affleck.
Michael B. Jordan was originally cast in the role of Marcus Belmont, but he dropped out due to scheduling conflicts.
Norman Reedus has a dog's paw tattoo on his hand, this is the emblem of the private military contractor company Blackwater. Reedus and Ejiofor's backgrounds in the movie was as ex special forces soldiers that had worked for the private company in Iraq. Blackwater was banned from operating in Iraq after an incident in which a number of civilians were killed. It has subsequently rebranded itself a number of times, but remains a shadowy presence in the Middle East and Africa.