Totalitarian governments in the early 20th century had three basic characteristics: 1- ruled by a single ruler (or party) with unrestricted power. 2- used violence and intimidation to maintain power. 3- people were not given political freedoms, and dissension was not allowed.
The totalitarian governments that existed around the time WWII began were Nazi Germany, Fascist Italy, the Empire of Japan, and the USSR (which was a US ally during the war). Lets use Nazi Germany as an example of how totalitarianism led to WWII.
Throught the 1930's, Germany was still recovering from the Treaty of Versailles, which blamed Germany for WWI and forced the Germans to pay reparations (money for damages) back to the allied powers. This, coupled with the stock market crash of 1929, bottomed out Germany's economy. Soon enough, the Weimar Republic that was ruling Germany was unable to truly raise Germany back to pre-WWI status. With its political, social, and economic climate in shambles, a strong political party like the National Socialist (Nazi) party was able to take control. When Adolf Hitler was given control of the Nazi Party, he was able to transform Germany into a totalitarian state- he was in complete control, he used intimidation and fear to maintain power, and no dissension was allowed.
Because France and Great Britain appeased Hitler and allowed him to take territory from the Czech Republic, Hitler continued to push for a Germany filled only with Aryans, those Hitler considered ethnically pure and truly "German". With a growing power and the strength of an entire nation behind him, Hitler and his totalitarian regime were able to invade more land, which eventually sparked war in Western Europe (this happened on September 1, 1939, with Germany's invasion of Poland).
While totalitarianism is not the only cause for WWII, it does help explain how Germany became powerful again after WWI and the Treaty of Versailles, and how that power enabled Hitler to begin his conquest of Europe.
The start of World War II was caused, in part, by the rise of totalitarian governments. Germany, Italy, and Japan all had totalitarian governments. For the most part, the leaders of these countries were free to do whatever they wanted. They talked about restoring pride in their country. They began to build up their militaries. They talked about undoing past wrongs. Germany wanted revenge for the Versailles Treaty. Italy felt it didn’t get enough land from the Versailles Treaty. Japan felt it was treated unfairly at the Washington Naval Conference because they could have fewer warships than Great Britain or the United States could have. These countries eventually formed the Axis Power alliance.
These countries eventually became aggressive. Japan invaded Manchuria in 1931 and China in 1937. Italy invaded Ethiopia in 1935 and Albania in 1939. Germany moved its military into the Rhineland in 1936. In 1938 and 1939, Germany invaded Austria, Czechoslovakia, and Poland. There were few voices within each country that would oppose these actions. When the Japanese Prime Minister opposed the invasion of Manchuria, he was assassinated. The rest of the world ignored these actions also.
As a result, these totalitarian governments and their leaders began to think they could do whatever they wanted. They felt they were invisible. they took nationalism to an extreme level. Totalitarianism was one of the causes of World War II.
This helped to lead to WWII because totalitarian countries like Nazi Germany and Japan were the ones who caused the conditions that led to the war. It is hard to say that totalitarianism itself caused the war since, for example, the USSR did not really cause the war to happen and it was totalitarian. However, it was the actions of totalitarian states that brought the war about.
Because Germany and Japan were totalitarian with strong military influences, their people were unable to exert any control over foreign policies. The expansionist leaders of both countries were able to take steps (taking Austria and Czechoslovakia and invading Poland; invading China) that caused the war.