When Xerxes invaded Greece, he was beaten by the Greek phalanx, the disciplined line of hoplites, armed with a spear and a shield. The hoplites were highly motivated because they defended their home turf, their own small farms. They were land owning peasants, with enough money to buy their own spear and shield. The Athens had changed their laws to give everybody land, and created a (sort of) democracy in doing so.
For long time, the most dominant factor on the battle field had been the chariot, which necessitated an aristocrat to ride it, because a chariot is expensive and needs servants to drive the horses and maintain it. As a result, according to William McNeill in the great book “The Rise of the West”, society in those years was aristocratic. In the Middle-Ages, the most formidable war machine in Europe was the heavily armored knight on horseback, again necessitating an aristocratic society. Due to the introduction of the fire weapons, and unavoidable, under Napoleon, mass conscription, war was made available for the masses again and power depended on the biggest and best organized armies. No coincidence that the ancient regime was wiped out and a constitution and democracy were introduced. The first world war was the pinnacle of mass armies running against each other, and saw the introduction of general voting, including women.
The last 100 years saw the introduction of the combustion engine and huge firepower, atomic bombs, satellites and computers. This has brought technology into the battlefield. Precision bombardments and laser guns. Internet warfare. At this moment an arms race in space is taking place. A late fad is the un-manned airplane, the drone, that spies on the enemy and occasionally can kill too.
This suggests that the dominant power now is technology. As a result we will see technocrats pulling the strings. The far majority of the Dutch House of Parliament now has a university degree. Kyoto protocols based on academic climate models determine our industrial policy. Governments don't dare to make a decision without think tanks calculating it in models into 3 decimals. The appointment of the new Greek and Italian technocrat governments, to solve the financial problems, is just a step.
Nerds rule the world!