What fueled economic growth but also enflamed old rivalries and contributed to two world wars?

The economic and political practice known as New Imperialism. This was a major policy in the advanced economies of the late 19th century that sought to expand themselves through territorial expansion and control over strategic resources on the nations of "less civilized" populations. The qualifier 'New' is used to differ it from the first european wave of expansion on the Americas since the focus of this second expansion was on the African and Asian continents. Historical examples of this policy are the british domination of India, known as the British Raj, and the german trading outposts in China such as that in Tsingtao (modern day Qingdao).    

president franklin roosevelt supported the tva as part of his first new deal measures approved by congress in 1933. this new agency was designed to control floods, produce electric power, and improve the lives of people living in the tennessee valley. the tva accomplished many of these goals despite problems.