anzus african century american century asian century bric brimc balance of power balance of power in international relations british empire chinese century cold war dutch golden age energy superpower geopolitics george modelski great power hard power hegemony hierarchy historical powers hyperpower middle power military alliance military power projection nato napoleonic wars netherlands new york next eleven polarity in international relations political power population portugal potential superpowers power in international relations power politics pyramid realpolitik regional power second anglo-dutch war second superpower shanghai cooperation organisation soft power soviet union spain superpower superpower collapse superpower disengagement transition treaty of versailles united states war