Andrew Bacevich has written  a withering review of Robert Kagan’s The World America Made:
Yet Kagan’s tacit attempt to trivialize the Iraq War won’t wash. Among other things, that sorry episode confronts us with a troubling fact: in today’s world, the most bellicose countries tend to be democracies, with the United States very much in the vanguard.
Kagan rehashes the cliché that “democracies rarely go to war with other democracies.” While offering reassurance that friendly relations between the United States and Canada are likely to endure, this dictum leaves unanswered a more pressing question. How is it that the magnanimous United States—which Kagan wistfully likens to “the catcher in the rye, preventing young democracies from falling off the cliff”—finds itself enmeshed in quasi-permanent war across large swaths of the planet?
Part of the answer to this question may be found in the way that Kagan and other democratists think about the relations between democracies and non-democracies. Kagan often inaccurately describes the latter as “autocracies,” but more important than the terms used is the assumption that there is a mutual ideologically-informed antagonism between competing political systems. In recent years, Kagan has imagined a multipolar world as a reversion to 19th-century great power politics, but he sees major powers competing in terms of ideological rivalry . One of the problems with this view is that the ideological rivalry is one-sided, and the authoritarian regimes are almost always on the defensive. Authoritarian regimes aren’t interested in exporting their political models, and they are only too happy to work with any kind of government, democratic or not, so long as it advances their perceived interests. Meanwhile, for some people in major Western democratic states, the mere existence of uncooperative or antagonistic authoritarian regimes is viewed as problem for Western democratic states to “solve,” which frequently involves subversion and may require the use of force.