You can also look at World War II as just an inevitable battle between empires. Japan was rising in the East, Hitler was rising in the West. Both empires were determined to dominate their hemispheres by force and secure the resources that were located there.
The empires in their way, the USSR, the United States, Britain and France had to ally themselves to stop Japan and Germany. That's how you ended up with such political enemies as Russia and the US on the same side in that war.
Welcome to the world of broad questions and wide ranging answers! In my mind, the start of World War II emerged with the ending of World War I and the Treaty of Versailles. In the attempt to ensure the horrors of the First World War were never to be repeated, President Wilson of America and other victorious European leaders imposed the harshest of terms on the nations that lost. The harshest of terms were reserved for Germany. The reality was that Germany was crushed at the end of the First World War and the terms imposed by the treaty made it nearly impossible for Germany to reemerge. This created chaos in its economy and political state. Without any strong form of guidance to emerge, it left the stage completely open for anyone to grow from a grass roots sentiment to gain power. Adolf Hitler understood this better than anyone else and began articulating his view of a proud and strong Germany, which began to resonate with Germans as they experienced a weak and impotent one. This message began to gain traction and Hitler assumed power and all the world was open to him. On a militaristic and national security front, Hitler began to assert that taking over lands which originally belonged to Germany, essentially rewriting the political borders imposed by the Versailles treaty, was essential for Germany to not engage in a protracted conflict and for Germany to reclaim her rightful identity. Due to the fact that most of the other European nations were both in the midst of economic crisis and political struggles themselves, trying to mend their own nations after the First World War, and that most other nations truly sought to prevent another conflict like it, they appeased Hitler by granting him his political wishes. Domestically, Hitler continued through legislation and law the process he articulated through social theory that there were specific "enemies" responsible for the weakness of Germany. Most of these scapegoats were individuals such as Jewish individuals and others that fell outside his articulation of social perfection. Essentially, they provided the internal enemy which could allow him to consolidate power and prevent examination of his own use of it. The growing advance of Hitler, his emergence and collaboration with other "smaller" dictators such as Mussolini of Italy and Franco of Spain, as well as Hirohito of Japan helped to form the Axis powers which would challenge the nations of Europe, and then America, in the Second World War.
Historians in the future will note the period in world history from 1914 to 1945 as a time of global warfare, with a 20 year intermission between the first and second acts. Although definitive dates may give us a specific time for historical actions, they can minimize the other minor events that led up to the major ones. Most would agree that the beginning of World War II commenced in 1939, if you hold a European or American point of view; but in the early and mid 1930's Japan had expanded into China as well as Southeast Asia and begun the subjection of other countries. Even considering the war in Europe beginning in 1939 is not quite accurate; Finland and the Soviet Union had began fighting in the mid 1930's. Even earlier, in 1922, France invaded Germany after the latter had violated terms of the Versailles Treaty. The span of time between 1918 and 1939 was not at all peaceable; all "intermission" meant was that major powers did not engage in all out warfare. However, these minor wars help to explain how the major conflict reignited, and underscore the fact that the Second World War was a result of the First World War, whose flawed and inadequate peace treaty left critical political issues unresolved. The tragedy of World War I was that the world had to fight World War II two decades later.
To further pohnpei's previous post:
Adolph Hitler's rise to chancellor of Germany in 1933 set the wheels in motion for what would eventually become WWII. In 1931, Japan had already initiated their takeover of Manchuria and the eventual capture of China's seaports. Hitler used the Spanish Civl War to test new weaponry and earn the alliance of Italy's dictator Benito Mussolini, who had already gained a foothold in Africa with his capture of Ethiopia. Hitler's annexation of Austria in 1938 began the military hostilities. Germany later captured Czechoslavakia, but it was not until Poland was invaded did Great Britain become involved. By this time, the Germany-Italy-Japan Axis was too powerful for the England-France alliance, and Hitler soon pushed his armies throughout Europe. The Soviet Union stayed out of the war by signing a neutrality agreement with Germany which allowed Josef Stalin to gain control of Russian border nations such as Romania, Finland, Latvia and Estonia.
Hitler's greed reached its apex when Germany voided its neutrality with Russia by sending three million troops to invade the huge nation in 1941. The Russians eventually held on, and German troop losses totaled more than a million. This setback, along with Japan's decision to attack Pearl Harbor, Hawaii, in December 1941 and bring the United States into the war, proved to be the beginning of the end for Hitler's hopes of total word domination. The combined Allied invasion of Europe--first in Sicily and then in Normandy, France--moved the war to its end less than one year after the decisive D-Day Invasion in June 1944.
This war was caused largely because Germany and Japan were unhappy with the way the geopolitical system was set up after the end of WWI.
Germany was unhappy because the Treaty of Versailles had treated it harshly. The Treaty told them they couldn't have much of a military, took parts of their territory away, and made them pay war reparations.
The Japanese felt that they deserved (and needed) an empire in East Asia and the Pacific.
Both of them started to try to fix what they saw as problems with the geopolitical order. When they went "too far" WWII started, first in Europe, then in the Pacific.
Perhaps if you had a more specific question...
World War II took place between1939-1945 and in which most of the countries of the world got involved. The number military people killed in World War II is estimated to be about 17 million. In addition there were civilian deaths due to causes such as starvation, bombing raids, massacres, and epidemics. The war took place in nearly every part of the world.
World War II began on Sept. 1, 1939, when Germany under leadership of Hitler invaded Poland. Up to June 1940, by which time Hitler had invaded Poland, Luxembourg, Denmark, Netherlands, Belgium, Norway and France, UK and its commonwealth allies were the only countries that opposed Hitler. At this time, Italy also joined the war on Germany's side. The fighting then spread to Greece and northern Africa, and in June 1941, Germany invaded the Soviet Union, drawing that country also in the war. On another front Japan attacked United States military bases at Pearl Harbor on December. 7, 1941, bringing the United States into the war. By mid-1942, Japanese forces overran much of Southeast Asia many islands in the Pacific.
The warring nations in the World War II was divided in two clear groups when Germany, Italy, and Japan formed an alliance known as the Axis, which was later joined by six other nations. On the other side, called allies, the United States, Great Britain, China, and the Soviet Union were the major powers> By end of the war number of allies had increased to 50. During 1942, the Allies were able to check the advance of Axis in northern Africa, the Soviet Union, and the Pacific. The allied forces then landed in in Italy in 1943 and in France in 1944. In 1945, the Allies were able to advance into Germany from the east and the west. In Parallel a series of battles in the Pacific enabled the Allied forces to reach Japan's doorstep by the summer of 1945. At this stage the war was clearly being dominated by Allies, forcing Germany to surrender on May 7. Japan also surrendered on September 2, 1945, after nuclear bombs were dropped on Hiroshima and Nagasaki.
the causes of World War II can be traced back to problems left unsolved by World War I (1914-1918), which created new political and economic problems. The hardships and humiliations faced by some countries subsequent to World War I, enabled some leaders to stir up national sentiments in these countries to assert their rights by force. These sentiments were then used by these leaders to try to fulfill their dreams of dominating the world.
In the 30's, in Germany, was a situation of severe economic crisis. Based on economic situation and population discontent, the German nation was waiting for a savior leader.This one was a mediocre and mentally ill individual, named Adolf Hitler,who relied on the Germans trust and used it to satisfy their ambitions and in benefit of German traditional industrial and militaristic society.
Hitler broke all treaties from the end of World War I and developed, together with German industrialists, arms industry to an unimaginable level in Europe. On the basis of this army, equipped very modern, Hitler began to develop the Third Reich, "empire of 1000 years", to the detriment of neighboring nations: Poland, Czechoslovakia and then entire Europe, with the price of millions of victims.
At the basis of this empire of evil stood revanchist ambitions to change the "status quo" imposed by the allies after the World War I, when Germany was brought to her natural boundaries.
These anomalous ambitions, supported by a whole dull nation, were shattered by European and the world countries, that could not accept their loss of independence, and Germany has suffered a division, after the Second World War,in two countries with different systems, capitalist and communist. Germany suffered and territorial losses of about one third of the territory, after the Soviet occupation (German eastern territories, like Prussia, was finally occupied by the Soviet Union).