Mission: Devil's Choice/Walkthrough

During the Cry Havoc mission, near the end you are prompted to set the chain reaction in motion. When you clear the room containing the console, you find it is behind a force field. In order to lower that force field, you must follow a corridor on the right side of that room back in to the room behind the console and kill the Elachi commander there. When he dies, the force field will drop, and you can return to the room with the console and start the chain reaction.