What provided the pretext for unleashing European rivalries?

Answer: The end of World War II united Europe and encouraged the process of decolonization.

Explanation:

After the destruction brought with it by other world-wide, the European countries have begun to reduce colonial tensions and thus began the process of decolonization.

The European colonial powers also had the favor of conquered lands during the war, so this was more reason to begin decolonization. The suffering that brought about the greatest war in human history has had a positive impact on people, so Europe sought to unite to avoid future conflicts.