In 1939 war finally began, causing the second global conflict. Many things had sparked World War II.
After World War I, Germany's pride was hurt, hurt because they were humiliated. And since their pride meant everything they would someday repay or regain their pride. So Germany's eager for revenge was high. As the present of communism was spreading towards the US, the threat of it came along with it. It wasn't only a threat to the US but to its religious freedom as well. Even though the threat of fascism was growing to the threat of communism out weighed it by a lot. So with the distraction of communism, Hitler's forces were able to build up. .
Germany's desire for revenge led them to attack a weakened country, France. France after the World War I wanted peace. And the German forces knew that France would not attack back. So Germany then invaded France causing the problems that sooner or later led to the 2nd World War. .
Although America remained neutral for a period of time they soon became involved in preventing World War II. Doing this by trying to give Hitler what he wanted while Hitler gave up on conquering other countries. But this did not work. Hitler did not give up causing countries to become madder at him for not following the deal. .
America's business may have led to WW II also, because America remained neutral. We remained neutral at the beginning because supposedly we were to busy ourselves. This also adds on the poor leaders of the Allies. If some of leaders would have tried to prevent Hitler from spreading anymore may have helped prevent war. .
The most important factor that started war was the invasion of Poland. The invasion led the rest of the world to become mad and upset with Hitler and his forces. If Germany would have agreed to the appeasement the break out of anger may have prevented the whole thing. Even though this was not the only thing that led to the war, it had a great impact.