Reddit reviews Power, Trade, and War

Dividing states to limit their power has been done. This can take many different forms, from outright division (Germany after WWII is one example) to simply taking away certain territories or colonies which are thought to increase power. In the case of Germany, the country had started two wars recently and was seen as particularly aggressive. Solving the "German Question" and preventing Germany from starting another war was thought to justify extreme measures in remaking German society. However, this strategy requires conquest of the country in question. In the case of the United States that is basically impossible due to the size of its military and the presence of its nuclear arsenal.

On the other hand, states which are too large for their own good, as opposed to the good of the rest of the world, divide themselves all the time. Internal divisions lead to violent or peaceful separation of part of the state. Rome did it peacefully and split in two. You're from the UK, so you might remember Ireland splitting off. Sudan is now two countries; the former Yugoslavia is now many. However, the difference between Germany and the above examples is that except in the case of Rome, there were major ethnic divisions that led to each country's breaking up, and in Rome, the problem was one of administration. These countries weren't split apart because they were too powerful, they split apart because the central government lacked the power to keep the country together.

Powerful countries don't just divide themselves, they have to be divided by outside forces. Although dividing powerful countries might lead to more peaceful outcomes, forcing them to do so would certainly involve a great deal of fighting. Also, the argument exists that a high concentration of power can actually lead to greater peace than some alternatives. Edward Mansfield wrote a very interesting book on the relationship between the distribution of power and the probability of war. I'd recommend you read it.