Economic conditions have historically been both a cause of war, both interstate

Economic conditions have historically been both a cause of war, both interstate and civil, and a cause of peace. What are the economic factors that lead to war? What are the economic factors that facilitate peace?
along with the second topic :
War is often rooted in multiple sources located at various levels of analysis. Select two levels of analysis (individual, state/societal, or global/systemic) and compare the contributions that theories at each level have made to our understanding of the causes of war.