This week, Iraq descended from instability into outright mortal crisis, as jihadists from ISIS (the Islamic State in Iraq and Syria, formerly known as al Qaeda in Iraq) swept into the country’s north and conquered Mosul, its second-largest city. The Sunni extremists are making their way southward, capturing cities along the way to the capital, Baghdad, where Iraq’s Shiite Prime Minister, Nouri al-Maliki, is scrambling for emergency powers to fight them off. So far, he’s had no success: the Times reports that Iraq’s Parliament “seems paralyzed” and has not even formed a quorum to vote for emergency powers, and the Guardian reports that earlier this week, 30,000 Iraqi Army troops “simply turned and ran in the face of the assault by an insurgent force of just 800 fighters.”

According to a range of observers and experts, there’s plenty of blame to go around for this situation. Much of it belongs to al-Maliki, Iraq’s ineffective and authoritarian leader. The New Yorker’s Dexter Filkins calls al-Maliki’s pro-Shiite policies “probably the dominant” factor driving Iraq’s collapse. “Maliki is a militant sectarian to the core,” Filkins notes, and with the Americans gone, there is no one to stop him “from acting brutally and arbitrarily toward Iraq’s Sunni minority”—pushing them into the arms of extremists. Slate’s Fred Kaplan agrees, in part: “The collapse of Mosul, Iraq’s second-largest city,” he argues, “has little to do with the withdrawal of American troops and everything to do with the political failure of Prime Minister Nouri al-Maliki.” Maliki, Kaplan writes, has “no interest in conciliatory politics on a national level,” which is why “he’s now facing a monumental, even terrifying armed insurgency,” and which also explains why his troops fled from the insurgents in Mosul: “they felt no allegiance to Maliki’s government; they had no desire to risk their lives for the sake of its survival.”

If poor leadership put Iraq at risk, events nearby catalyzed the current disaster. “Even with Maliki, Iraq might have limped along for a time,” writes Daniel Benjamin of the Brookings Institution, “but the Syrian civil war hastened the crisis.” The insurgents’ spoils from Mosul and other cities will help its fight both “in Iraq and on its other front in Syria, where it will deepen the fight against Bashar al-Assad and his allies from Lebanese Hezbollah. And, completing this vicious circle,” its victories in both countries “will help it draw more recruits, especially from abroad.”

Intelligence expert Bruce Riedel, also of Brookings, offers perspective on what the organization will do as it gains recruits, arms, and more land. Even before taking Mosul, ISIS “had already seized most of Anbar province in Iraq and Raqqa province in Syria. There, it enforces a Taliban-style extreme version of Islam. Mosul represents a much bigger price, an ancient city with great symbolic value. ISIS is effectively creating a stronghold across the Syrian desert in the heart of the Arab world, erasing the borders set a century ago by the British and French after the fall of the Ottomans.”

Over the long run, it’s the erasure of these borders that probably frightens U.S. policy-makers the most. Although the Obama Administration is understandably reluctant to re-involve the United States in Iraq, it must also fear the consequences of watching the country’s teetering government gradually lose control over greater and greater swaths of its territory. The risks of that outcome are familiar enough. As Brookings’s Daniel Benjamin soberly reminds us: “Lesson number one of foreign policy in the twenty-first century ought to be: Allow no states to fail, ungoverned spaces to emerge, terrorist safe havens to be established.”