When Baker discovers Allen and Garnett dead in the original game, seven shells can be seen next to the 'death pistol', indicating it was fired. However, in Hell's Highway, Garnett is killed before firing a shot with the pistol.
At the beginning of "Tooth and Nail" after receiving a mission briefing from Col. Sink, S/Sgt. Matt Baker salutes Sink.
Soldiers never salute officers in a combat theater because doing so could identify the officer to any enemy snipers who could be watching. A seasoned combat veteran NCO like Baker would know better.
During a cut scene one of characters performs CPR on a gunshot victim by using the chest compression method. The chest compression technique was not developed until 1960.
When Baker's 1911 is being reloaded, the guide rod under the barrel is seen to protrude to the length of the barrel. Full-length guide rods for the 1911 didn't come out until the late 1970s.
In Operation Garden, Friar says "I'm out. Gotta reload." Zano replies, "Hooah, get it done."
"Hooah" is a term that started being used in the Army in the late 1990s.