- Ottoman Empire for centuries;
- Britain and France from WWI until the 1950s/1960s;
- US and Soviet Union during later Cold War;
- US since end of Cold War;
- currently: US, Russia
- US on way out, largely;
- Russia ambitious but lacks economic power;
- China, other Asians reluctant, far away and unwilling to enter into regional conflicts;
- Europeans too weak and unwilling