Some have questioned whether Friedman's thesis is 100 percent true, mentioning NATO air strikes against Yugoslavia as a potential exception.
If NATO didn't exist today, no one would propose creating it.
Almost three-quarters of all defense spending occurs within NATO countries, meaning the alliance is largely the only military show in town.
Unless one can somehow imagine NATO countries going to war with each other, such as Belgium invading the United Kingdom, it is hard to see how "world wars" could escalate outside of NATO member countries.
If NATO is responsible for the bulk of the world's military spending and NATO no longer has the stomach for full-on war with modern states, then large-scale war seems less likely.