Although the initial U.S. air strikes provided the refugees breathing space, the Islamic State still basically has the initiative. Ironically, Obama the multilateralist has not yet followed George H. W. Bush’s roadmap after the first Persian Gulf War in assembling an international coalition to achieve his humanitarian objectives. In April 1991, Kurdish refugees fled Saddam Hussein’s repression, and Bush persuaded the U.N. Security Council to adopt Resolution 688, declaring the refugee flows a threat to international peace and security. He then launched Operation Provide Comfort, later supplemented by aid to the Shiites in southern Iraq.Today’s ongoing tragedy would have been entirely avoidable had Obama not withdrawn U.S. forces from Iraq in 2011. By so doing, he eliminated a considerable element of U.S. leverage in Baghdad, one that had significantly limited Iran’s ability to expand its influence inside Iraq. With substantial U.S. forces still present, Iraq’s various ethnic and confessional groups were more likely to make progress knitting together a sustainable national government and to lessen their profound, longstanding mistrust, which existed well before the Islamic State erupted from Syria.

We must now decide on U.S. strategic objectives in light of the dramatic, albeit still-tenuous, territorial gains by the Islamic State; the unfolding disarray in Iraq’s government; the grinding conflict in Syria; and the looming threats to stability in Lebanon, Jordan, and Turkey. This will require some unpleasant choices, as well as recognition of the obvious reality that many policy options are simply unavailable until Obama leaves office in 2017.

America’s basic objective is clear: We must seek to destroy the Islamic State. It is simply not enough to block the group’s threat to the Kurds or other vulnerable minorities in the region. The risks of even a relatively small “state” (or “caliphate,” as they proclaim it) are chilling. Leaving the Islamic State in place and in control only of its current turf in Iraq and Syria (including northern-Iraqi hydrocarbon deposits and associated infrastructure) would make it viable economically and a fearsome refuge for terrorists of all sorts. Just as Afghanistan’s Taliban gave al-Qaeda a base of operations to launch terrorist attacks culminating in 9/11, a similar result could follow if the Islamic State successfully erased and then redrew existing boundaries.

But, many ask, how can the Islamic State be removed from the territory it now holds without U.S. combat forces’ being centrally involved? Aren’t we too “war weary” to do much of anything? Perhaps, but this is surely a debate worth having. And that debate’s central “organizing principle,” as Hillary Clinton might say, is this: The United States must prevent a new terrorist state from emerging in the Middle East. Period.

If there are American political leaders who are truly content to have this embodiment of evil consolidate its current position, let them say so unambiguously. The vast majority of Americans, however, will be profoundly concerned at the likely consequences for America, Europe, Israel, and our Arab friends in the region if we do nothing. After the Holocaust, we said “Never again,” not “Well, maybe a little.”

Assuming the Islamic State is decisively defeated (a heroic assumption, given Obama’s passivity), what happens next? In Syria, non-radical Sunni Arabs, while still hoping to oust Bashar al-Assad, are increasingly beleaguered, both by regime forces and by the Islamic State and other radicals. In Iraq, the attempted coup of Prime Minister Nouri al-Maliki, who until recently was backed solidly by Iran, has added to the disarray. His reluctant decision to step aside as prime minister, however, has only removed him from the stage; it has neither reduced Iran’s dominance nor changed the fundamental political disarray among Iraq’s factions. Maliki’s maltreatment of Iraq’s Sunnis aroused such opposition that tribal leaders and former Baathists initially joined with the Islamic State because of their common contempt for the national government. What outcome can we now achieve that would satisfy non-radical Sunnis, not to mention us?

Unavoidably, therefore, we must identify what is doable in Iraq rather than what is desirable. We are long past the point of debating “one Iraq” versus “three Iraqs,” because fierce animosities have already split Iraq de facto into Kurdistan and the predominantly Arab remainder. The only outstanding issue is whether the Arab lands will themselves break into two, one largely Sunni, the other largely Shiite.

As things stand, helping to create three Iraqs looks to be America’s best option. Our metric today, looking forward, is not whether the Platonic ideal of a unified, democratic Iraq might once have been achieved, or might yet be achieved unknowable years hence. Instead, we must proceed on the clear-eyed basis of what America’s interests are now, choosing among less-than-ideal options. …

Until we effectively counter Iran’s increasing dominance in Shiite Iraq — indeed, until we overthrow the ayatollahs in Tehran — we cannot ignore the reality that Iraq’s Sunnis simply will not tolerate domination by an “Iraqi” government Tehran controls in every material respect. Similarly, as with their opposition to al-Qaeda in Iraq during the 2006–07 “surge,” most Iraqi Sunnis have no desire to trade Iranian-backed repression for Islamic State repression. …

While we must prevent the Islamic State from forming a new, independent terrorist state composed of Sunni Arabs, there is an acceptable alternative. In broad strokes, a transborder state carved out of Iraq’s and Syria’s current territory is far from undesirable, and is in any event increasingly likely. If rightly established and led by Sunnis acceptable to the United States and our regional allies, a new Sunni state is entirely realistic.

It would mean partitioning Syria, an outcome some have predicted, and leaving Assad with essentially an Alawite enclave in Syria’s western and coastal regions. A stable, “moderate” Sunni state with control over oil assets in northern Iraq equitably divided with the Kurds would also serve to protect Jordan’s eastern border. Northern areas with significant Kurdish populations could join Iraqi Kurds in their new state, and Sunni Arabs would have the rest.

Concededly, this is easier said than done, and drawing new boundaries will be arduous and perhaps ultimately futile. Moreover, creating a new Sunni state will not solve the problem of Iran’s continuing to dominate the regimes governing the rump portions of Syria and Iraq. These projections of Tehran’s power would still threaten those states’ neighbors and provide Iran much-needed allies. Unfortunately, however, Syria’s Assad dictatorship and Iraq’s successor to Maliki will remain relatively secure until the ayatollahs lose power in Tehran.

Regarding Syria, many who advocated aiding the anti-Assad opposition will now contend that, once the Islamic State is on the run, we should seize the moment to topple the dictatorship. The hard reality, however, is that for over three years the Syria conflict has been a strategic sideshow in the larger struggle against Iran. If a moderate, transborder Sunni state emerged, fighting an Assad regime confined to an Alawite enclave would not be worth the risks of Obama’s stumbling around simultaneously confronting Russia and Iran, which both back Assad. If Iran’s ayatollahs and Revolutionary Guards were to fall and be replaced by anything like a sensible government, Assad (not to mention Hezbollah and Hamas) would lose his biggest source of financial and military support. To be sure, Russia would still see Assad as an ally, but without Iran, even Moscow might recalibrate its stakes in Syria. And until Iran flips, as long as Assad retains Russian support, Obama cannot be trusted to face off competently against Moscow.

Any real opportunity to stitch the pieces of Iraq back together will come only when the mullahs next door are eliminated. Unfortunately, however, while most Iraqi Shiites oppose Iran’s domination, they have been ineffective in preventing it, and there is little prospect that this pattern will change.

Obviously, the central problem is not Iran’s surrogates, but Iran itself, America’s main regional adversary. And until the United States confronts the ever more pressing need for regime change in Tehran, we can hardly expect others in the region to have the strength or the will to arrange things to suit our interests. Obama’s obsession with securing a nuclear-weapons deal means the odds that he would support overthrowing the ayatollahs approach zero. The regime is determined to possess nuclear weapons, so appeasing it in Syria, as Obama has done, was never going to cause Tehran to modify its positions in the nuclear talks. Far better to concentrate on regime change in Iran by overtly and covertly supporting the widespread opposition and watch Assad fall as collateral damage thereafter.