Lebanese are justifiably frustrated that Friday’s attacks in Paris overshadowed the bombings that killed 43 people in Beirut City the day before. But equal respect for human life isn’t the only reason Western media should be more focused on Beirut than they have been.

The Paris attack succeeded in frightening the West, but the attack on Beirut represents a more important strategic avenue for Islamic State. The Sunni-militant group isn’t going to destabilize France. Yet destabilizing Lebanon, a tinderbox at the best of times, is an achievable goal.

If Lebanon were to devolve into civil war, it would become an obvious zone for Islamic State to expand its reach. And who, exactly, would go to war to defend Lebanon?

To understand the strategic objectives of the Beirut bombings, begin by putting yourself in the shoes of the planners. Almost all of Islamic State’s successes have come under identical circumstances.

In essence, the group’s trademark is to exploit the vacuum in weak or crumbling states. This includes Syria, where civil war rages, and the Sunni area of Iraq, where the Baghdad government’s writ barely ran even before Islamic State took over. It also includes those far-flung places where self-declared affiliates have sprung up to exploit power vacuums, particularly Libya and Afghanistan.

In Egypt, the state is relatively strong, but Islamic State nevertheless is challenging it at its weakest points. The bombings in August of government security facilities in Cairo, attributed to Islamic State, were intended to push Egypt into chaos. Since then, the downing of the Russian jet, almost certainly carried out by Islamic State affiliates in Sinai, has revealed this strategy further by raising questions about Egypt’s ability to function as a sovereign state that protects air travel.

Lebanon is a far more fragile state than Egypt. And it has a far greater advantage as an Islamic State target: Its proximity to the Syrian battlefield. Right now, the group has no direction in which it can plausibly expand its territory except Lebanon. Turkey, Jordan, Iran and Saudi Arabia are all strong states that won’t countenance the loss of land. Lebanon, however, is vulnerable to civil war, which would create the vacuum Islamic State needs.

So if you were an Islamic State planner, how would you go about precipitating that civil war? A pretty good start would be bombings in Shiite-majority neighborhoods in or near Beirut — like Bourj el-Barajneh, the southern suburb where Thursday’s attack took place. Like most of Lebanon, the suburb isn’t composed of only one denomination. There are also Sunnis and Christians there, as well as refugees.

The most dangerous fault line in contemporary Lebanon is between Shiite Hezbollah and Sunni groups. The paradigm of Lebanon’s past civil war wasn’t Sunni-Shiite, but the regional dynamic of that tension casts a long shadow over the country today.

There are fewer Lebanese Christians than there once were, because of immigration and relative population growth. And Druze remain a significant force in the country. So there are potential stabilizers with a common interest in avoiding Sunni-Shiite confrontation. But as we know from Iraq, all it takes for the new kind of violence to emerge is for it to become clear that the state can’t do anything about it.

Lebanon’s leaders have held a delicate balance for more than a quarter-century, notwithstanding periods of Syrian domination and the gradual rise of Iranian-backed Hezbollah. But circumstances can change, the way that the influx of Palestinians and PLO leaders from Jordan after the Black September conflict of 1970-71 disrupted Lebanon’s balance and helped precipitate civil war.

There are more than 1 million Syrian refugees registered in Lebanon, and the actual number may well be half a million higher. Seen through this lens, it’s pretty remarkable that Lebanon hasn’t already fallen into civil war. That may be attributed partly to ordinary Lebanese knowing just how costly conflict would be, and partly to the fact that the Syrian refugees mostly just wanted to avoid conflict.

A cynic might say that Hezbollah maintains enough control in its areas of the country to dissuade other militias from standing up against it. It’s possible that Sunni militias in the cities of Tripoli and Sidon have calculated that they would lose in any direct conflict, considering the tremendous support Hezbollah gets from Iran.

Nevertheless, provoking Shiite reaction against Sunni civilians might leave both sides unwilling or unable to maintain the rational calculus that so far kept them from violence. Certainly Islamic State’s best strategy is to break that implicit understanding.

And if Lebanon went hot, there would be no regional ally to step in and protect it. Iran could be expected to increase its support for Hezbollah, but without committing its ground forces. The Syrian military, such as it is, has its hands full. Russian planes are in the zone, and could conceivably intervene on behalf of Hezbollah, but it’s unclear how much they could do.

Turkey, the U.S. and Saudi Arabia would probably be unwilling to do any more than they are already doing against Islamic State. For them, the further expansion of the group’s territory isn’t that much bigger of a problem than its simple existence.

The wild card is Israel, which would like to avoid having Islamic State on its northern border. Yet given that the alternative is Hezbollah, the Israelis would be hard-pressed intervene. Their experience occupying Lebanon is not one they would want to repeat. In truth, Israel’s strategic interest in a Lebanese civil war would be to see Hezbollah weakened while assuring that it ultimately prevailed.

The real winner in a Lebanese civil war would almost certainly be Islamic State, which would have a new vacuum to exploit. Which is why the world should be paying more attention to the death and destruction in Beirut.

By Noah Feldman

Noah Feldman, a Bloomberg View columnist, is a professor of constitutional and international law at Harvard University and the author of six books, most recently “Cool War: The Future of Global Competition.” — Ed.

(Bloomberg)