I just read a review in the paper by Jake Coyle, The Associated Press, where in the second sentence, he describes it as "Sam Mendes's technically dazzling Second World War tale". Here's some basic history: the Second World War ran from 1939 to 1945, although the US stayed out of it until Pearl Harbor. The First World War was from 1914 to 1918, and the US didn't show up until 1917. The level of ignorance that would allow that error to make it past various editors and into print is truly breathtaking.