Robert Kagan's realist irrealism

From Kagan's piece (h/t S. Lemieux) in New Republic (which I've bookmarked for actual reading, as opposed to skimming, later):

In fact, the world “as it is” is a dangerous and often brutal place. There has been no transformation in human behavior or in international relations. In the twenty-first century, no less than in the nineteenth and twentieth centuries, force remains the ultima ratio. The question, today as in the past, is not whether nations are willing to resort to force but whether they believe they can get away with it when they do. If there has been less aggression, less ethnic cleansing, less territorial conquest over the past 70 years, it is because the United States and its allies have both punished and deterred aggression, have intervened, sometimes, to prevent ethnic cleansing, and have gone to war to reverse territorial conquest. The restraint showed by other nations has not been a sign of human progress, the strengthening of international institutions, or the triumph of the rule of law. It has been a response to a global configuration of power that, until recently, has made restraint seem the safer course.

The first sentence is obviously correct: the world is indeed an often brutal place. The second sentence, particularly the second part of it, is  more questionable. And the portion in which the "U.S. and its allies" are credited with the decline of territorial conquest is very, very incomplete (to put it charitably), and w/r/t the GW Bush admin, downright weird. Territorial conquest (of the 19th/20th-cent-and-before sort) has declined because most states (I said "most" not "all") are no longer interested in conquering territory. It's not something their leaders think about and plan for. They know (they have learned) that invading other countries does not, as a rule, tend to solve their problems. That's a main reason why territorial conquest has declined since WW2, imho, though there are also other reasons, which I've written about here before.