Seventy-five years ago, on 1 September 1939, Germany invaded Poland. With political agreements in place to come to Poland's aid, Britain and France both declared war on Germany within two days. It was the start of a conflict that would erupt over every continent and see the deaths of tens of millions of people, with much of central Europe destroyed. It would also see the development of jets, intercontinental missiles, computers and the Atomic Bomb.1939,...