When I first began research into religion and global politics, I began by trying to approach it as I had most of my previous research: canvas previous efforts, formulate some new conjectures, and then seek out real-world evidence that might test them. It didn't work.
The main problem was that there was simply too little previous work to build on. Beginning in the early 1980s, the discipline of international relations had fallen victim to a rather large blind spot. The nationalist-inspired violence of the early 1990s was its first manifestation, and religiously-inspired violence has proven to be its second. Simply put, the discipline tended to define rationality in such a narrow way that it was forced to shuffle off nationalism, civil war, guerrilla war, terrorism, and religious violence into the error term: violence spawned in such contexts wasn't of sufficient magnitude (compared to, say, a major conventional war, or a superpower thermonuclear exchange), and in addition, such "irrational" actors made poor foundations for general theories -- which were, and in many ways remain, the Holy Grail of international relations scholarship.
Consider two of the core texts that international relations (IR) scholars read as graduate students in the late 1990s: Hans Morgenthau's Politics Among Nations and Kenneth Waltz's Theory of International Politics. Neither provides anything meaningful by way to understand how religion might operate. In fact, Morgenthau waves his reader off of religion and ideas more generally, while Waltz doesn't mention it all. Power and how it was distributed among states was the key to explaining international politics. All else was in the service of that power. If nationalistic or religious ideas entered the fray, they were viewed as instrumental means employed by statesman to gain more power.
There was thus little by way of theoretical literature that could help an IR scholar understand the crucial links between religion, religious actors, and religious action in global politics. One might ask just how different these dynamics are. Clearly, power and power politics remain much as described by historians and theorists at least as far back as Thucydides. But the devil resides in the differences between what we have traditionally assumed as rational behavior and what we see in the real world. It took the better part of two decades to recover the rational bases of the nationalist-inspired violence that followed the end of the Cold War (and which continues today). Nationalists proved neither purely instrumental, cynically harnessing 'ancient hatreds' to increase power or hold on to valuable offices, nor swooning, hot-headed romantics, willing to sacrifice their own lives and the lives of thousands of their fellow nationals on a whim. Patient research, my own included, made clear that although we do encounter such motivations at the extremes, the vast bulk reside in the middle.
We should perhaps expect no less difficulty where theorizing about religiously-inspired violence is concerned, but two important points are in order here. First, religiously-inspired actors are rational, but like nationalists, their rationality is different. It follows that second, we need not avoid theorizing about religious actors because their rationality differs from our common understandings.
That said, what remains is to convince a broad audience that the study of religion and politics -- and in particular religiously-inspired violence -- is crucial; and that building general theories about religious violence can illuminate important features -- not only of religiously-inspired violence -- but of organized violence more generally.
I and (at present) a small number of colleagues have already undertaken much of this work, but by way of conclusion, allow me to introduce a bit of the empirical side of contemporary religion and politics. Three features in particular are worth noting.
First, religion is not necessarily the sole driving force of much of the large-scale violence we see today. Nationalism remains a powerful peer competitor. Since 1940 only about one-third of all civil wars had a religious basis, and of these only about half featured religion as a central issue. However, if you look at the nature of ongoing civil wars, half of them now have religion as an element. More often than not religion is married to nationalism. Religion alone is rarely the sole culprit.
Consider the 1979 Iranian Revolution, which is about as close as we get to a religiously-motivated political event. A common narrative interferes with our understanding of what happened. That narrative invokes the image of religiously-inspired (read: irrational), hot-headed mobs spontaneously rising to overwhelm and overturn established order (the international news media remain somewhat complicit in this: when was the last time you can remember seeing "Iranians" on TV doing anything other than glowering, shouting, or threatening?). But had the Shah not previously made such a hash of Iran's economy and political system, revolution would not have succeeded. The country was ripe for revolution; whether religiously-inspired or not. Ayatollah Khomeini and his followers were enterprising, and acted strategically: they returned from exile just in time to tip the already tottering apple cart (just as Vladimir Lenin did in Russia in 1917). Even in this case, religion and religious motivation were only part of the story. It is this aspect of unraveling religion and its role in violence that has made research into the dynamics so complex and frustrating, yet exciting.
Second, even where religion is only part of the story, it seems (and we need more research to understand why and how) to make the conflict more intense and more harmful to noncombatants. Such conflicts are also less likely to end short of total victory by one side over another (but this is not necessarily a bad thing in the longer term -- I just finished a book exploring why this is the case).
Third, just as religious civil wars in the aggregate may not be the most common type of civil war since 1940 (the current decade aside), religiously-motivated acts within a civil war may be rare. More recently I have begun researching the nature of violence in the Caucasus region of the Russian Federation, disaggregating violence motivated by religion from that which is not. It turns out that for the period of 2000-2008, only four percent of the violence can be attributed to religious (Islamist) actors with a purely religious motivation. Yes, that is correct, four percent -- and this during a period in which a supposedly Islamist-supported civil war (if Russia is to be believed) was raging in Chechnya.
On the other hand, this four percent of violence was more fatal. And, as a proportion of all violence, religiously-motivated violence increased over the period. The same pattern appears to hold true for religiously-inspired suicide terrorism. Research by Assaf Moghadam, for instance, has shown that religiously-motivated suicide terrorism (largely of the Salafi-jihadist variant) resulted in higher casualties than similar attacks motivated by other concerns; and that as a proportion of activity, has been increasing over the past decade.
In sum, religious actors are as apt to be rational in a broader sense as nationalist, and even state actors. The nature of this rationality needs to be explained in the service of accounting for the tendency of religiously-inspired violence to be more intense than violence inspired by other motivations. Moreover, as the Chechnya case highlights, it is not only from concern that irrational actors make poor foundations for general theories that we haven't had sufficient research, but also from the extreme political utility of framing one's adversaries as irrational: who respects limitations of force against, for example, "wolves?" (It is no accident that animals of various sorts are frequently chosen by states to characterize their adversaries.) Recovering the rationality of our adversaries thus forces us to recognize their humanity, and by extension, to both acknowledge our own failings to treat them justly, and acknowledge limits on how we may act toward them. Understanding religion, religion and politics, and religiously-inspired violence in these terms makes the enterprise as necessary as it is rewarding.