The origins of realist IPE theory can be traced back to mercantilism.
Mercantilism was a doctrine of political economy employed by European empires between the 15th and 19th centuries.
Mercantilists believed global wealth was finite and thus viewed the international political economy as a ‘zero-sum game.’
State A’s gain is State B’s loss
Consequently, mercantilists believed states ought to compete with and block the economic interests of its rivals.