The Second World War began in September 1939 when the German Leader, Adolf Hitler, invaded Poland. Britain and France went to war to help Poland, but by July 1940 German armies had overrun most of Europe, forcing the British army to evacuate from Dunkirk to England. From airfields in Norway, Denmark and France, Hitler was now able to launch air attacks on British towns and cities.

Even before the war, the Germans had prepared target maps and photographs of the objectives they wished to attack - not only army camps, airfields and naval dockyards but also industries that helped the British war effort. The chemical works in Castleford shown here was one such target for air attack.