In the "On Track" mission, in the town square there is wanted poster for Jimmy Patterson in a German disguise, complete with reward for his capture.
When you go to Holland in the third mission, you come across a paratrooper named Corporal Langteau from the 82nd Airborne. Langteau is the surname of one of the writer/directors.
When you dress up as a cook and sneak into the mansion, look at the paintings on the wall. One of them is the Girl With A Pearl Earring.
The starting level is D-Day when all the British, Canadian, American, and French troops fight the war against the Nazis. In The Diary Of Anne Frank (the book), they talk about the Normandy Landings (D-Day), and we can relate to this. As we know, this happens earlier before the Franks received the news.