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; it saw the deaths of tens of millions of people, much of central Europe destroyed, the development of jets, intercontinental missiles, computers and the Atomic Bomb. 1939 saw the first display of the German Blitzkrieg in Poland, along with the deployment of RAF squadrons to France and the first bombing raids over both Germany and the UK. There had long been omens to show the ways that war in the air would develop, with the Germans honing their Blitzkrieg tactics in the Spanish Civil War and the Japanese bombing civilian populations in China. This book is the first in a series covering the Second World War in the air year by year.