The Nationalist forces were drawn from every political element in Spain opposed to the government – the Falangists, Carlists, Alfonsine monarchists, the bulk of the professional military, and (though not in organized form) the ‘autonomous right’. The Falangists were that element which had the most in common with Italian fascism, but even the Falangists had some serious disagreements with Mussolini (much less Hitler).

I think of the Abraham Lincoln Brigade as genuinely heroic if also slightly naive;

No, red haze nuisances fighting for a crummy cause.

But there’s a larger problem with your post, one often apparent in attempts by secular, western leftists to understand Islamism. You have projected your own frustrations with current conditions and your own aspirations for a different, better future onto Islamist volunteers. How do you know they share them? Or should we consider different motives–the desire, for instance, to hold women as sex slaves, which, by all accounts, has been an important motivating factor and a major part of the ISIS recruiting drive?

Couple of quick points. First, Obama administration policy in re Syria has been quite conscious, istm, of the limits of what an “empire” can do in a situation that is very complicated and confusing and resistant to easy manipulation. Recently the admin is realizing it needs to do a little more, but it’s still not a massive intervention. The air strikes vs ISIS have supported indigenous resistance to ISIS, and thus seem justified. ISIS’s own long-term military prospects are not especially favorable to it (or so argues a recent guest post on my blog by someone who has been following the situation).

Second, it might be nice if historians, instead of citing only what their fellow historians (in this case C. Maier, Frederick Cooper, and J. Burbank) have written about empire, would take a look at the large lit. on empire(s) produced by IR scholars, political scientists, and sociologists. I’m not saying you haven’t done that; I’m just struck that the two works on empire mentioned in this post are by historians. Not that the concerns are necessarily different, inasmuch as some of the work on empire by political scientists or sociologists also focuses on “a more analytic understanding of why empires, including modern Western ones, tend to experience certain kinds of recurrent crises and … fall prey to some of the same self-defeating uses of violence and injustice” as other political forms do.