Bomber Command’s night offensive against Nazi Germany, which lasted for nearly six years, was one of Britain’s major contributions to the Allied effort during the Second World War. But the decision to conduct its main operations at night only came about following heavy losses by day, when its prewar medium bombers had been found lacking in modern air warfare. The Luftwaffe, too, had its early problems. Initially without a dedicated night fighter, it was ill-equipped to defend the Reich, and so the stage was set for what would become one of the most critical strategic encounters of the war.