In September 1939, England and France declared war on Germany, reacting to Hitler's attack on Poland despite their warnings. This was the result of a delayed but ultimately resolute decision to oppose the expansionist policies of both Germany and Fascist Italy, policies made manifest by their occupation of foreign territories from the mid-1930s on. As in the case of the First World War, the causes of the new conflict went back to the contest between the great European powers to share, each for its own benefit, the wealth of their neighbours and of their colonies. Besides, the humiliation and the unbearable 'reparations' imposed on Germany after the end of the First World War nurtured Fascist ideology and precipitated the outbreak of the Second World War.

The 'Blitzkrieg' - as Hitler's early victories were called - ended with the Germans occupying most of Europe, while the attack on the Soviet Union underlined Hitler's plans for a united Nazi Europe. Wherever the Germans prevailed, the countries of Europe came to know the 'New Order', which meant the political submission of the conquered states to Germany, the deprivation of all freedoms, economic looting, persecution and the Europe-wide elimination of Jews and other 'undesirable' ethnic groups, such as the Gypsies. From 1941 on, when Japan, the third ally of the Axis, attacked the American fleet at Pearl Harbour thus paving the way for the occupation of the whole of southeastern Asia, the conflict became international.

From 1942 the countdown for the Axis powers began. The Soviets, with the victory at Stalingrad, immobilized the German troops and proceeded to launch a powerful counter-offensive, while the Germans were also in their turn crushed by the Allies in Africa. The Allied landings in Italy (July 1943) caused the downfall of Mussolini while the landing at Normandy (June 1944) led to the liberation of France. Finally, on 8 May 1945, Germany, razed to the ground and conquered by the Allies, surrendered. In August 1945 Japan was forced to surrender as well, after the Americans had dropped atomic bombs on the cities of Hiroshima and Nagasaki. The Second World War ended, putting the final seal on an entire era and ushering the whole world into a new time, deeply scarred by its experiences.