The rise of aggressive nationalism among some of the nations defeated in World War I.
The rise of communism in Soviet Russia, which was seen as a threat by many European nations.
Explanation:
These are the two factors that led to the beginning of World War II. In the years before World War II, communism gained acceptance in Soviet Russia, and this new ideology was seen as a threat by many European nations. Moreover, nationalism also became popular among many countries, and this led to the development of more aggressive and extreme fascist governments.
