"Vargas"

Captain "Brewer" is a British SFSG troop who appears in Call of Duty: Modern Warfare 3: Defiance.

Mission
In the mission "Overwatch", "Vargas" along with Capt. "Brewer" and Sgt. "Wilson" are sent to infiltrate a warehouse that is suspected of being a Russian weapons cache.

Real identity?
"Vargas", "Brewer" and "Wilson" are actually British SFSG troops, however, in the previous missions they are portrayed as US National Guard and the next mission after the mission they are featured in, they are portrayed once again as US National Guards. It is most likely that these troops were meant to be entirely different troops, but were named the same as the US National Guards by mistake.