Nearly two millennia ago, the Romans built the Arch of Triumph in Palmyra, Syria. According to Picturesque Palestine, Sinai, and Egypt, published in 1881, “The wonder in these ancient ruins is not that so much has fallen, but that anything remains.” Last week, ISIS blew the Arch of Triumph, which the group considers idolatrous, to pieces. Such acts of aggression and barbarism have mobilized a vast enemy coalition, which includes almost every regional power and virtually every great power (and notably the United States, often compared to the Roman Empire in its hegemonic strength). Yet, incredibly, this alliance seems incapable of rolling back the Islamic State. How can a group of insurgents declare war on humanity—and win?

One of the basic principles of military strategy is that the attacker needs preponderant force to win. “It is the rule in war,” wrote Sun Tzu in The Art of War, “if our forces are ten to the enemy’s one, to surround him; if five to one, to attack him; if twice as numerous, to divide our army into two. If equally matched, we can offer battle; if slightly inferior in numbers, we can avoid the enemy; if quite unequal in every way, we can flee from him.”

ISIS has thrown this rulebook out the window by declaring war on one adversary after another—and then striking them with inferior numbers of troops.

In 2011, ISIS (then under the name of the Islamic State of Iraq) intervened in the Syrian Civil War and attacked the regime in Damascus, along with its allies (Iran, Russia, and Hezbollah) as well as moderate and Islamist Syrian opposition forces. In 2014, with the outcome of the Syrian conflict still in the balance, ISIS launched a major offensive into Iraq, thereby massively expanding the opposing coalition to include Iraq, Iranian-trained militias, the United States, Britain, and France. Unperturbed, ISIS then struck Kurdistan, and the ranks of its enemies swelled further.

By conventional logic, the militants’ strategy is reckless and even suicidal—the design of an apocalyptic cult with a death wish.

On one side of the battlefield there’s ISIS, with its tens of thousands of fighters.

On the other side of the battlefield is the anti-ISIS coalition, which includes four out of five permanent members of the UN Security Council (the United States, Russia, Britain, and France). Even the sole holdout, China, has signaled it may aid the Iraqi regime through intelligence-sharing and arms sales. The coalition also includes most regional players: Turkey, Syria, Iran, Iraq, Jordan, and the Gulf states. Did I mention that the most powerful non-state actors in the region, including Hezbollah and the Kurds, are also arrayed against ISIS?

In 2014, ISIS brought in estimated revenues of just over $1 billion. In the same year, the U.S military budget alone was $580 billion. Heck, each year the U.S. military spends about half of ISIS’s revenue just on marching bands. The anti-ISIS coalition has an enormous edge in both quantity and quality of troops, including formidable air power and surveillance capacity.

On paper, this could be the greatest mismatch in the history of war. And yet after a year of U.S. bombing, ISIS has fought the coalition to a draw, by maintaining its core territory and expanding its control into Anbar province in Iraq and Palmyra in Syria. In September, Martin Dempsey, then chairman of the Joint Chiefs, said the battlefield was “tactically stalemated.”

Why can such a grand military coalition do no better than a tie? A lot of attention has been paid to ISIS’s innovative tactics: its “shock and awe” suicide bombings, horrific decapitations, and social-media campaigns. But it’s also worthwhile to consider why seemingly strong coalitions are often much weaker than they look.

ISIS is not the first revolutionary group to take on the world and overcome the odds. In the 1790s, revolutionary France fought Austria, Prussia, Britain, Russia, Holland, Spain, Portugal, and Piedmont in Italy. For the next two decades, France defeated its adversaries and created a vast European empire—until Napoleon Bonaparte finally overreached with the invasion of Russia.

A century later, from 1917 to 1922, the young Bolshevik regime in Russia battled domestic White Russian opponents, as well as an international coalition that included the United States, Britain, France, Canada, Australia, and Japan. Despite facing a seemingly insurmountable challenge, the Red Army emerged victorious.

Each case is unique, of course. But the inability of coalitions to suppress revolutionaries in France, Russia, and now the Middle East stems from three common forces: disinterest, disunity, and discourse.

The first problem is disinterest. The revolutionaries have a greater stake in victory than the coalition does. The militants are singly focused on winning the contest in question. By contrast, members of the coalition face a wide range of competing security threats all over the world. The coalition may have more power, but the revolutionaries have more willpower.

During the Russian Civil War, for example, the Bolsheviks were fixated on victory, whereas the allies fighting them were distracted by other issues, had less resolve, and withdrew from Russia one by one. Similarly, for ISIS today, its military campaign is an existential issue that occupies its constant attention. But defeating ISIS is not of vital interest for most of the group’s enemies. Not for Russia. Not for France. Not for the United States. Among U.S. officials, the ISIS threat jostles for attention with other challenges, from the conflict in Ukraine to the rise of China. The United States wants to defeat the Islamic State, but it doesn’t want to pay a high price for victory.

The second problem is disunity. Wartime alliances are often far less than the sum of their parts. Like a chain gang tied together at the ankle, the coalition lumbers along at the pace of its slowest member, moving at cross-purposes and continuously tripping over itself.

During the French revolutionary and Napoleonic wars, France repeatedly outmaneuvered the divided and squabbling European coalitions assembled against it. Napoleon pursued a “strategy of the central position” where he situated his troops between opposing forces, striking one adversary and then the other before they could unite. In World War I, the Allied general Marshal Foch commented sardonically: “Now that I know about coalitions, I respect Napoleon rather less.”

Syrian President Bashar al-Assad is focused on shoring up his rule and even appears to have deliberately facilitated the rise of ISIS to make his regime look like a lesser evil to domestic and foreign audiences. Russia and Iran want to maintain the Syrian regime in power, whereas the Saudis insist that Assad must leave office. Turkey is worried about the Kurds. The United States only recognizes certain members of the anti-ISIS coalition as true allies, and deeply distrusts Russian intentions in Syria. The result is a dysfunctional war effort plagued by internal feuding. By comparison, ISIS seems a model of unity: a single entity with a coherent command structure that can move forces from one front to another.

The third problem is discourse, or the weaker side’s ability to seize the narrative. When Paris defied all the monarchs of Europe, it seemingly confirmed that the ideas of liberté, égalité, and fraternité were an unstoppable, world-changing force—inspiring French troops to carry the tricolore into foreign lands. “A man does not have himself killed for a few half-pence a day or for a petty distinction,” said Napoleon. “You must speak to the soul in order to electrify the man.”

Similarly, when the victors of World War I intervened in the Russian Civil War, it seemed to prove Lenin’s claim that the capitalist states were determined to strangle the revolution at birth—steeling the Bolsheviks’ resolve.

In the case of ISIS, the more enemies the group faces, the more fodder it has to argue that Western infidels are dead set on oppressing Sunni Islam, and that the insurgents are God’s instrument, destined for victory. Plus, with so much material power, the anti-ISIS coalition faces the tyranny of high expectations. Anything less than rapid success indicates failure. By contrast, ISIS is the underdog. Fighting virtually every great power and holding its own looks like an incredible achievement.

So yes, the anti-ISIS alliance may be one of the grandest in history. It may also be the most disinterested and disunited, and the most vulnerable on discourse. The coalition is riven by petty distinctions. ISIS speaks to the soul.