This question is vague. Please specify who did intervention with whom and when and where. I have never heard of any intervention being done in World War 2. I could see it happening between General Patton and Field Marshall Montgomery and General Bradley.
1. World War I and the treaty of Versailles 2. Adolph Hitler
It was one of the 4 major reasons of war, the other three are Alliances, Militarism, Nationalism.
The US was across an ocean from the European countries, which was a major reason why they decided to stay out of war.
it would kill many people
Machine Gun
The major cause the first world war the Assassination of Archduke Franz Ferdinand of Austria and his wife by Gavrilo Princip Other reasons are secondary.
Russia's involvement in World War I was draining the country's resources.
World War I, World War II, and the moon landing are major world events.
texas annexation ,mexican-american war, spanish-american war
Roosevelt's intervention emphasized America's growing role in world affairs.
Non-intervention
the major reasons World War 2 ended would be because Adolf Hitler commited suicide(April 1945).Then 2 atomic bombs hit Hiroshima in August 1945.Then Japan surrenders on August 14 ,1945.Thats the only info i got sorry if it don't please you!