Well, first of all, nationalism is not so much a movement as an extreme form of patriotism, that facilitated the rise of movements such as the nazi party.
I assume that the affect that nationalism played on Germnay would have a very great role in answering this question. After the treaty of Versailles, which ended World War One and imposed extremely harsh penalties on Germany, the country was humiliated and impoverished. This fostered an extreme sense of nationalism in the country, which fed into the philosophies of political parties that advocated a return to order and a stronger, respected Germany. This also led to a mutation of nationalism, into racism, anti-semitism, homophobia ect.
Furthermore, nationalism was a major cause of world war one. Nations began an arms race, putting the safety and status of their own country above that of the safety of the world at large.
Hope this helps a bit!
good luck for ur exams!!!.......