The Second World War was the largest and most costly conflict in terms of human lives in the whole history. The total number of victims is estimated at 60 million people. The war (in fact, wars) fought between 1939 and 1945 involved literally the entire planet. At its peak more than 50 million men and women serving in the armed forces and two-thirds of the gross domestic products of the most affected countries were used to finance the conflict. The war was not only the result of a serious imbalance in world politics, but also the direct result of deep hostility and violent imperial ambitions derived from the First World War of 1914-1918, which can be traced back to the origins of the next, more extensive and devastating. Starting from 1919 all attempts to create a stable world order seemed, from the start, doomed to failure. In East Asia, China suffered a collapse of the political and Japan began to slowly expand at the expense of the Chinese. In the Mediterranean and the Middle East, the end of the Ottoman Empire gave way to the imperialist ambitions of Mussolini's Italy, intending to rebuild a new "Roman Empire". In Europe, the Bolshevik Revolution of 1917 gave rise to a permanent atmosphere of social crisis, when the Treaty of Versailles caused extensive political resentments, which contributed to the rise of Hitler and the disruption of the balance of power at the end of the thirties.
The Second World War was the last in a long series of conflicts that had affected Europe from the seventeenth century. England and France wanted to keep their colonies, while Italy, Japan and Germany wanted to create their own. Were these imperial ambitions to give rise to the most disastrous campaigns of the war: German hostilities against the Soviet Union and the Japanese ones against China.
Britain and France went to war after the Nazi invasion of Poland in September 1939, but the Anglo-French efforts to stem the rising violence of imperialism were vain: in the space of a few weeks in the summer of 1940, they were defeated by German forces, largely thanks to the innovations of war made up possible by the airplane and the tank, weapons whose potential had become clear by the end of the First world War. Used in combination with radio communications, these weapons supplied to the armies mobility and impressive power, able to ensure rapid and effective victories. Slowly he found a way to counter, or at least limit, the devastating effect of these invasions, however, were the determining factor is the German offensive is allied. By September 1940 the three new imperialist powers (Germany, Italy and Japan) had signed the Tripartite Pact. In the course of the following year they embarked in a series of vast conflicts of imperialist character: Italy attacked Greece and tried to oust the British from North Africa and the Middle East; in June 1941 Germany invaded the Soviet Union; on January 1942, Japan had occupied most of Southeast Asia and the Western Pacific. The result of these wars of conquest was to join other countries to prevent a radical and violent change in the world. England, still unbeated but unable to stop the advance of Germany, was joined by the Soviet Union and, in December 1941, the United States. This alliance proved to be just enough to stop the advance of imperialism and the victory obtained only after four long years of, costly and devastating conflict. The ultimate success was achieved for many different reasons. The Soviet Union won the war after learning how to organize their own ground forces in a similar manner to the Germans and thanks to a huge war effort, involving all sectors of society and of economy. England and the United States, focusing its efforts in order to minimize losses, managed to gain control of the seas and the skies. The Allied strategy was centered on the bombing, following which claimed the lives of hundreds of thousands of Germans and Japanese. The control of the seas also allowed the West to move men and equipment in a flexible way and blocking vital supply routes of the enemy. When Britain and the United States landed in Europe, the defeat of Italy and Germany was now a foregone conclusion. Japan did not even have to be invaded: the strength of the Japanese was broken by the use of two atomic bombs in August 1945. The first direct consequence of the final defeat of imperialism was the stabilization of a new world order. Britain and France had to give up the empires for which had fought. Communism took control of much of Asia and Eastern Europe, while the United States used their economic and military power to protect their interests in the non-communist countries. The war produced a precarious and unstable peace, but at the cost of the suffering of hundreds of millions of people, involved in spite of themselves.