Russia's annexation of Crimea, and the rising tensions between east and west, marks an era of heightened competition between rival imperial powers, argues Rob Ferguson.
Russia, the US and the European powers are facing their greatest clash since the Cold War. Following the overthrow of Ukrainian president Yanukovich, the new pro-Western government in Kiev turned to seal a partnership with the EU and Russia annexed Crimea, home to the Russian Black Sea fleet and its route to the Mediterranean.
Tensions are spreading to other "buffer" states on Russia's southern borders. Barack Obama has called on EU leaders to increase their military spending.