As representatives of 68 countries participating in the global coalition to defeat the Islamic State (ISIS, ISIL, Daesh) meet in Washington, a number of plans will be on the table, and even more will be debated informally on the sidelines. As allied forces anticipate the liberation of Mosul, attention is increasingly focused on the next phase, both in Iraq and in Syria.

My American Enterprise Institute colleague Fred Kagan and his wife and frequent collaborator, the Institute for the Study of War’s Kim Kagan, recently unveiled a plan in the Wall Street Journal calling on the United States to create a Sunni Arab force along the Syria-Iraq border. That force would take on the Islamic State in Syria while building enough on-the-ground credibility to then negotiate a favorable post-conflict deal. They wrote:

The second major flaw in America’s strategy against ISIS, which is Sunni, is Washington’s reliance on non-Sunni and non-Arab partners. That amplifies the terror group’s message. In Iraq the U.S. works with the Shiite-dominated government, whose past persecution of Sunni Arabs fueled ISIS’s rise. Meanwhile, America’s Kurdish partners in both Iraq and Syria are pursuing an independent Kurdistan, a political goal that is unacceptable to most Arabs.

The U.S. has no meaningful presence among the Sunni Arab tribes in Iraq and Syria that ISIS, al Qaeda and others are vying to control. This appears to confirm al Qaeda’s claim that it is the only effective armed force dedicated to protecting Sunni populations from a combined assault by all the world’s powers. That message may win out if Washington does not rapidly change its approach… The key is finding new Sunni partners and taking the fight to new terrain, specifically, southeastern Syria, where ISIS leaders have refuge. American military forces will be necessary. But the U.S. can recruit new Sunni Arab partners by fighting alongside them in their land. The goal in the beginning must be against ISIS because it controls the last areas in Syria where the U.S. can reasonably hope to find Sunni allies not yet under the influence of al-Qaeda. But the aim after evicting ISIS must be to raise a Sunni Arab army that can ultimately defeat al-Qaeda and help negotiate a settlement to the war.

Kagan and Kagan are correct to castigate the ambivalence and acquiescence of the Obama administration to Iran’s role in Iraq and Syria. But, let’s be clear: Creating a sectarian, Sunni Arab militia is wrong.

Firstly, it ignores the poor U.S. track record of training armies and militias. Consider the $25 billion training program, sponsored by the Pentagon, for the Iraqi military and Kurdish peshmerga: The fall of Mosul and the rapid disintegration of the U.S.-trained Iraqi forces showed it to be an expensive failure, one that would have been a career killer for a general less media-savvy than David Petraeus. The subsequent effort to train Syrian rebels to take on the Islamic State proved no better.

Secondly, it substitutes a cartoonish image of the Popular Mobilization Units (Hashd al-Shaabi) for reality. While the Hashd al-Shaabi are often described as Shi’ite militias, they are actually far more diverse and have become an umbrella organization in which Christians and Sunnis also fight. Indeed, that diversity rather than reinforcing sectarianism should be the goal. There is a problem with Iranian influence among some of the Hashd al-Shaabi groups, but it is important not to throw the baby out with the bathwater and instead address the Iranian problem head-on.

The problem with the Kagans’ proposal, at least as it relates to Iraq, is that it would simultaneously reinforce Iranian propaganda by depicting themselves as the only savior of the Shi’ites while encouraging the Iraqi Sunnis continue to refuse the political compromises. The bombs detonating in Baghdad—both before and after the rise of the Islamic State—were not perpetrated by Shi’ite militias but rather by Sunni sectarian rejectionists.

Nor is it easy simply to will responsible Sunni Arab leadership into existence. Petraeus tried and ended up simply fueling more insurgency as he empowered former Baathists who pretended to support the United States right up until the money ran out.

The situation is no better in Syria. The Syrian Kurds—perhaps the most effective fighting force against both the Islamic State and al-Qaeda—have no desire to hand back the territory they have won at tremendous cost in blood. It is naïve to believe that the creation of a new ethnic and sectarian force would curtail rather than fuel further conflict.

There is no magic formula for Iraqi governance, but the Iraqis have built institutions which work for Iraq. The Hashd al-Shaabi may not be ideal but, alongside the Iraqi army, they are a structure more durable than what Petraeus and others earlier tried to create. To bring stability to Iraq, it is essential to encourage their further integration into a force that represents Iraq’s ethnic and sectarian diversity and to weed out those who place foreign loyalties above Iraqi nationalism.