Poland suffered more than any other country in the Second World War. One in six Poles died at the hands of the Nazi occupiers, and the Jewish population was wiped out. But Poland was only the trigger for a war which in two years was to engulf the world. Using rare and remarkable film from the conflict, Global War seeks to answer some of the most perplexing puzzles of the war: why did Hitler call off the invasion of Britain and turn instead on the Soviet Union? And why did he declare war on the USA in the winter of 1941? This film ties together the separate strands of the series and tells the tragic story of how a local conflict developed into a global war.