but not a determination.
I would say what makes the time pretty unique is, that

• the most advanced economies have a demography which simply does not need nor sustains empire like expansion. The Romans wanted an empire in 0. Napoleon wanted it, the German Kaiser, Hitler, and Stalin wanted it, Dshingis Khan, the Ottoman califs,.... Most people in the current developed world don't.
  
• distances in todays world still matter. A world hegemon is by far not a self evident outcome compared with more regional developments. The EU e.g. shows, that this has not to be violent. Sure the EU is unique in a sense up to now, but ASEAN or the AU perhaps take a similar direction. Long range transport of military equipment is very energy intensive, especially if it must be fast. (FAZ wrote last weekend, that inland water transport has an energy need proportional to speed^(3.5)) That's really nasty for oversea military operations.
  
• the weapons you named make it nonsense to start open conflict. So far leaders have acted very reasonable.
  
• there can be more than 2 parties, which cancel each other out. UK was not a hegemon in Europe in 1900. With a simple politics of balance of power - ally with the weaker - there is no need for a hegemon. Sure, this is not necessarily a long-term stable situation, but today there are so many international contracts, that I guess it is much more stable than ever before.
  

The outlined problem in the diary is resolved in a capitalistic system. You give the resource to the person who is paying the most. My personal guess is, that the European countries with their very low level of military spending as a share of GDP are doing exactly the right thing. There will be no serious war in the foreseeable future and the big armies some other countries have are just resource drags.

Der Amerikaner ist die Orchidee unter den Menschen
Volker Pispers