The main argument of this book is that wars tend to lead to bigger states with more stability (and even police) and this reduces violence. It's a useful and often entertaining history of war and how it played its part in the development of civilisation.
Violence began 400 million years ago when the first predators appeared. Human society, as we know it, began about 10,000 years ago when the last ice age ended. Because human evolve culturally change can happen much more quickly than in other forms of natural selection. This has applied particularly to ways of making war – the invention of better ways of killing people. But, paradoxically, this has reduced rather than increased the numbe of violent deaths.
When humans became farmers it became more sensible for conquerors to make them part of their new nation rather than destroy them. Conquerors became “stationary bandits”. Every revolution/war made it necessary for “leviathan” to get stronger – resulting in a reduction in violence.
In the 18th century Britain emerged as the first “globocop”. Humans had developed from small bands of foragers via Leviathans to produce a globocop. Eventually pax brittanica produced so many rivals of successful industrial development that Britain was ousted as a result of 2 world wars. The USA emerged as the new globocop.
The big question today is the relationship between a growing China and the US. The US economic problems are a serious threat to world peace. But climate change may be an even bigger uncertainty.
The book finishes with some rathe fanciful speculation about the impact of computers and robots for future war.