The following is meant to provide an overview of the military situation in Iraq for non-experts.

Caveat. It is exceptionally difficult to understand the dynamics of ongoing military operations. Oftentimes, the participants themselves do not know why they are winning or losing, or even where they are in control or where their troops are. For non-participants, it is often equally difficult to gain more than a rudimentary sense of the combat without access to the sophisticated intelligence gathering capabilities—overhead imagery, signals intercepts, human reporting, etc.—available to the United States and some other governments. As one of the CIA’s Persian Gulf military analysts during the 1990-91 Gulf War, I noted the difficulty that many outside analysts had in gauging the capabilities of the two sides and following the course of operations because they did not have access to the information available to us from U.S. government assets. Consequently, readers should bring a healthy dose of skepticism to all such analyses of the current fighting in Iraq, including this one.

Likely Next Steps in the Fighting

What appears to be the most likely scenario at this point is that the rapid Sunni militant advance is likely to be stalemated at or north of Baghdad. They will probably continue to make some advances, but it seems unlikely that they will be able to overrun Baghdad and may not even make it to the capital. This scenario appears considerably more likely than the two next most likely alternative scenarios: that the Sunni militants overrun Baghdad and continue their advance south into the Shia heartland of Iraq; or that the Shia coalition is able to counterattack and drive the Sunnis out of most of their recent conquests.

It is not a coincidence that the Sunni militants made rapid advances across primarily Sunni lands. That’s because it is not surprising that the Iraqi Security Forces (ISF) would crumble in those areas. As Baghdad has (rightly) observed, several of the divisions in the north were disproportionately composed of Kurds and Sunni Arabs, many of them frustrated and alienated by Prime Minister Maliki’s harsh consolidation of power and marginalization of their communities. They were never going to fight to the death for Maliki and against Sunni militants looking to stop him. Similarly, the considerable number of Shia troops in the north understandably saw little point to fighting and dying for principally Sunni cities like Mosul, Tikrit, Bayji, etc.

Baghdad could be another matter entirely. First, it is a vast city of almost 9 million people compared to Mosul with less than 2 million. Moreover, the Sunni militants only secured the western (Sunni Arab) half of Mosul, leaving the eastern (Kurdish-dominated) half alone. Conquering a city the size of Baghdad is always a formidable undertaking when it is defended by determined troops.

After the battles of the 2006-2008 civil war, Baghdad is also now a more heavily Shia city—probably 75-80 percent of its population, although it is very difficult to know for certain. While it is understandable, even predictable, that Shia troops would not fight and die for Sunni cities, many are likely to find their courage when they are defending their homes and families in Baghdad and the other Shia-dominated cities of the south.

In addition, as has been well-reported, the (largely-Shia) remnants of the ISF are being reinforced by Shia militiamen and bolstered by contingents of Iranian Revolutionary Guards. Although many of the Shia militiamen will be new recruits answering Ayatollah Sistani’s call to defend their community, others are hardened veterans of the fighting in Iraq in 2006-2008 and Syria since 2011.

Thus, the Sunni militants are likely to come up against a far more determined and numerous foe than they have confronted so far. The most likely outcome of that fighting will be a vicious stalemate at or north of Baghdad, basically along Iraq’s ethno-sectarian divide. That is also not surprising because it conforms to the pattern of many similar intercommunal civil wars. In Syria today, in Lebanon in the 1980s, Afghanistan in the 1990s, and elsewhere, that is where the frontlines tend to stalemate. They can shift here and there in small ways, but generally remain unchanged for years. That’s because militias in civil wars find it far easier to hold territory inhabited by the members of their identity group than to conquer (and hold) territory inhabited by members of a rival identity group. It’s one reason they typically try to “cleanse” any territory they have conquered of members of the rival identity group.

If military developments in Iraq conform to this most likely scenario, they could lead to a protracted, bloody stalemate along those lines. In that case, one side or the other would have to receive disproportionately greater military assistance from an outside backer than its adversary to make meaningful territorial gains. Absent that, the fighting will probably continue for years and hundreds of thousands will die.

Watch Anbar. So far, the Sunni militants in Anbar are the dog that hasn’t barked, at least not yet. Obviously, the Sunni militants have significant strength in Anbar, including considerable numbers of ISIS fighters. It is militarily obvious that they should seek to develop a complimentary offensive out of Anbar. Doing so would allow them to (1) open another axis of advance against Baghdad and catch it in a classic pincer movement, or (2) develop a direct advance against the great Shia religious cities of Karbala and Najaf (the most sacred sites in Shia Islam), and/or (3) force the Shia to divert military assets away from the north-south Sunni advance and potentially overstretch their manpower and command and control.

Consequently, the fact that no such offensive has yet materialized is noteworthy. It may be that Sunni militant forces in Anbar were so badly beaten up in the fighting with the ISF around Fallujah and Ramadi that they are not capable of mounting such an attack. Alternatively, they may be preparing to do precisely that.

In short, Anbar bears watching because a Sunni offensive there will further stress the Shia defenses. It is a key variable that could undermine the Shia defense of Baghdad. So if you are looking for something that would push Iraq from the most likely scenario (a bloody stalemate in or north of Baghdad) to the second most likely scenario (a continued Sunni advance through and beyond Baghdad) a successful Sunni offensive from Anbar would be one such variable.

Kenneth M Pollack Former Brookings Expert Resident Scholar - AEI

Watch Iran. Given the various problems on the Shia side (demoralization, fragmentation, politicization of the ISF), the variable that would be most likely to advantage the Shia and push Iraq from the most likely scenario (a bloody stalemate in or north of Baghdad) to the third most likely scenario (a Shia counteroffensive that eliminates most of the Sunni gains) is Iranian participation. On their own, it is unlikely that even the larger and more motivated Iraqi Shia forces now assembling to defend Baghdad would be able to retake the Sunni-dominated north. What would make that far more possible would be much greater Iranian involvement, particularly much larger commitments of Iranian ground combat formations.

So far, Iran appears only to have committed three battalion-sized groups of Quds force personnel. Quds force personnel are typically trainers and advisers, not line infantrymen. They are the “Green Berets” of Iran, who help make indigenous forces better rather than fighting the fight themselves. That would make sense for the current situation in Iraq, and those personnel will help stiffen the Shia defense of Baghdad. However, they are unlikely to improve Shia capabilities to the point where they can develop a major offensive to take back the North. Only the commitment of large numbers of Iranian line formations—infantry, armor and artillery—could do that. Consequently, were we to see a large Iranian commitment of such ground combat units, it would signal that the third-most likely scenario was becoming far more likely.

The Combatants, Part I: The Sunni Militants

It is important to understand a few key points about the Sunni militant side of the new Iraqi civil war.

It’s a Coalition, not a Single Group. First, ISIS (the Islamic State of Iraq and Syria) is essentially the “lead dog” of a larger Sunni militant coalition—hence my preference for the latter, more accurate description. ISIS has been fighting in conjunction with a number of other Iraqi Sunni militant groups. Effectively the entire rogue’s gallery of Sunni militias from the 2006-2008 civil war have been revived by Prime Minister Maliki’s alienation of the Sunni Arab community since 2011. AQI, the Naqshbandis, the Ba’th, Jaysh al-Muhammad, Ansar al-Sunnah, and all of the rest are back in operation in Iraq, in at least tacit cooperation with a number of Sunni tribes.

These groups are key members of the Sunni militant coalition. They have done a great deal of the fighting, dying and occupying. Often they are indistinguishable from one another to outsiders or even Iraqis who are not themselves Sunni militants.

It’s an Iraqi Entity, not a Foreign Invasion. While the Iraqi government has emphasized the foreign elements in ISIS, their indigenous, Iraqi component is of far greater importance. ISIS has been part of the violence in Iraq for over a year. Many of its personnel are Iraqis. Even before last week’s operations, it had an extensive network in Iraq which both conducted terrorist attacks across the length and breadth of the country, and has been engaged in a conventional battle for Ramadi and Fallujah with the ISF for over six months. Moreover, it is busily engaged in recruiting and training additional Sunni Iraqis which is simply reinforcing the Iraqi nature of the group. Finally, as noted above, ISIS is only one piece (albeit, the central piece) in a larger array of Sunni groups that are overwhelmingly Iraqi.

This is important because Prime Minister Maliki and his apologists have tried to paint ISIS as a group of foreigners who were waging the Syrian civil war and suddenly decided to launch an invasion of neighboring Iraq. If that narrative were true, it would suggest that a pure (and immediate) military response were warranted since such a group would have a great deal of difficulty holding territory conquered in Iraq. It would obviate the need for far-reaching political changes, which Maliki seeks to avoid.

Consequently, it is critical to understand that ISIS is as much an Iraqi group as it is Syrian or anything else, and its success is largely a product of its ability to capitalize on Iraq’s political problems and to be accepted (if only grudgingly) by many Iraqi Sunnis as a champion in the fight against what they see as an oppressive, partisan Shia regime.

These are Militias First and Foremost, Terrorists only a Distant Second. Here as well, Prime Minister Maliki and his apologists like to refer to the Sunni militants as terrorists. Too often, so too do American officials. Without getting into arcane and useless debates about what constitutes a “terrorist,” as a practical matter it is a mistake to think of these groups as being principally a bunch of terrorists.

The problem there is that that implies that what these guys mostly want to do is to blow up buildings or planes elsewhere around the world, and particularly American buildings and planes. While I have no doubt that there are some among the Sunni militants who want to blow up American buildings and planes right now, and many others who would like to do so later, that is not their principal motivation.

Instead, this is a traditional ethno-sectarian militia waging an intercommunal civil war. (They are also not an insurgency.) They are looking to conquer territory. They will do so using guerrilla tactics or conventional tactics—and they have been principally using conventional tactics since the seizure of Fallujah over six months ago. Their entire advance south over the past week has been a conventional, motorized light-infantry offensive; not a terrorist campaign, not a guerrilla warfare campaign.

And right now, they are completely consumed with continuing to wage this conventional offensive against the Shia forces arrayed against them. That is likely to remain their pre-occupation for some time to come. Somewhere down the road, they probably will begin to mount terrorist attacks against other countries from their secure areas in Iraq and Syria, precisely as the intelligence community warned. But that will be an adjunct to their waging of the new Iraqi civil war.

That is important because defining the Sunni militants as terrorists implies that they need to be attacked immediately and directly by the United States. Seeing them for what they are, first and foremost a sectarian militia waging a civil war, puts the emphasis on where it needs to be: finding an integrated political-military solution to the internal Iraqi problems that sparked the civil war. And that is a set of problems that is unlikely to be solved by immediate, direct American attacks on the Sunni militants. Indeed, such attacks could easily make the situation worse.

The Combatants, Part II: The Shia Coalition

A few points are also in order regarding the other side of the fight, the Shia.

Of greatest importance, we need to recognize that the Iraqi Security Forces are fast becoming little more than a Shia militia. This trend began 3-4 years ago when Prime Minister Maliki began to push Sunni and Kurdish officers out of the armed forces, to replace them with loyal Shia officers. As a result, even before the current debacle, the ISF had become far more Shia than it had been, with fewer and fewer Sunnis and Kurds. Even before the dramatic events of last week, most Sunnis and Kurds referred to the ISF as “Maliki’s militia.” Since last Tuesday, we have seen large numbers of Sunni Arab and Kurdish soldiers desert the ISF, leaving an even more homogeneously Shia force. There are still Sunnis and Kurds in the ranks and in the officer corps, but that seems likely to dissipate over time.

This is a trend that is common to these kinds of intercommunal civil wars. The “Syrian Armed Forces” of today are nothing more than the Asad regime’s militia, heavily comprised of Alawis and other minorities aligned with the regime. All throughout the Lebanese civil war, there was an entity called “the Lebanese Armed Forces” (LAF) that wore the uniforms, lived on the bases and employed the equipment of Lebanon’s former army. But they had become nothing but a Maronite Christian militia (after all of the Muslims and Druse deserted in the late 1970s), and their commanders nothing but Maronite Christian warlords. The same is already happening with the ISF and that trend is likely to continue.

This is important because one of the worst mistakes the United States made in the 1980s was to assume that the Lebanese Armed Forces were still a neutral, professional armed force committed to the security of the entire state. That was a key piece of the tragic U.S. mishandling of Lebanon. When the Reagan Administration intervened in Lebanon in 1983, one of its goals was shoring up the LAF so that it could stabilize the country. Everyone else in Lebanon—and the Middle East—recognized that the LAF had devolved into a Maronite militia and so they saw the U.S. intervention as the (Christian) United States coming to aid the (Christian) Maronite militia. That is why all of the other warring groups in Lebanon immediately saw the American forces not as neutral peacemakers, but as partisans—allies of the Maronites—and so started to attack our forces. It led directly to the Beirut barracks blast and the humiliating withdrawal of our troops.

There is the same danger in Iraq. If we treat the ISF as an apolitical, national army committed to disinterested stability in Iraq, and provide it with weapons and other military support to do so, we will once again be seen as taking a side in a civil war—even if we are doing so inadvertently, again. Everyone else, including our Sunni Arab allies, will see us as siding with the Shia against the Sunnis in the Iraqi civil war. That perspective will only be reinforced by the ongoing nuclear talks with (Shia) Iran. It is why any American military assistance to Iraq must be conditioned on concrete changes in Iraq’s political structure to bring the Sunnis back in and limit the powers of the (Shia) prime minister, coupled with a thorough depoliticization of the ISF . That is the only way we may be able to convince the Sunnis that we have not simply taken the side of Maliki and the Iranians.

What happened to the ISF? Many have been asking what happened to the Iraqi Security Forces that brought them from the successes of 2007-2008 to the collapse of their units in northern Iraq last week. Obviously, a definitive answer to that question will only be provided by historians at some future date, but a number of factors have been known about the ISF for some time and these undoubtedly caused the collapse in part or whole.

First, it is important to recognize that the ISF built by the U.S. military in 2006-2009 had only very modest military capabilities (primarily in counterinsurgency/counterterrorism/population control operations). Throughout the modern era, Arab militaries have never achieved more than middling levels of military effectiveness and on most occasions, their performances were dreadful. Iraq was no exception. (Those looking for additional information on this may want to read the chapter on modern Iraqi military history in my book, Arabs at War.) This was largely a product of factors inherent in Arab culture, education and economics. With enormous exertions, a small number of Arab militaries overcame these problems to perform at a mediocre level. However, whenever Arab regimes politicized their armed forces to try to prevent a military coup against themselves, the performance of their armies dropped from bad to abysmal.

American military trainers and advisors were able to marginally improve the military effectiveness of the ISF by introducing rigorous, Western-style training programs and partnering closely with Iraqi forces in ways that allowed U.S. personnel to get to know their Iraqi counterparts. As a result of this familiarity, over the course of many months, the Americans figured out who were the good Iraqi soldiers and who were the bad, who was connected to the terrorists or militias, who was connected to organized crime, who was smart and brave, and who was lazy or cowardly. And the U.S. military then went about systematically promoting the best Iraqis, and pushing out the bad ones.

The greatest impact of these American efforts with the ISF in 2006-2009 were to depoliticize it, both to modestly increase its combat effectiveness and to make it professional, apolitical and therefore accepted as a stabilizing force by all Iraqis. Again, this was largely performed by promoting professional, patriotic Iraqi officers and removing the sectarian chauvinists. The U.S. also pressed Baghdad to accept more and more Sunni and Kurdish officers and enlisted personnel into the ranks. As a result, the ISF became a far more integrated force than it had been, led by a far more apolitical and nationalistic officer corps than it had been before. Indeed, in 2008, when Prime Minister Maliki sent heavily Sunni brigades from Anbar down to Basra to fight the Shia militia, Jaysh al-Mahdi, the Shia of Basra welcomed the ISF brigades and fought against the Shia militiamen.

Unfortunately, despite the boost it gave him, Prime Minister Maliki saw this largely apolitical and professional military as a threat to himself. He feared that it was overrun by Ba’thists (he sees far too many Sunnis as closet Ba’thists), unwilling to follow his orders (despite the fact that it had always done so), and looking to oust him at the first excuse. So, beginning in 2009-2010, he began to remove the capable, apolitical officers that the United States had painstakingly put in place throughout the Iraqi command structure. Instead, he put in men loyal to himself, often because they had been the ones passed over or removed by the Americans. The result was a heavily politicized and far less competent officer corps.

Perhaps not surprisingly, Maliki’s officers saw little need for the rigorous training programs the Americans had put in place. They closed many of the training facilities we built and allowed training to fall by the wayside. Not surprisingly, when these formations got into action again—both in some skirmishes with the Kurds and more bloody fights against Sunni militants—they did very poorly, undercutting morale.

Finally, beginning in 2011 immediately after the departure of the last American soldiers, Maliki began to use his new, politicized ISF to go after his political rivals, many of them leading (moderate) Sunni leaders. This was a critical element in his alienation of Iraq’s Sunni community, and further demoralized the Sunni Arab, Kurdish, and other minority personnel in the ISF. It also disappointed many of the Shia soldiers and officers who preferred to be part of an apolitical, national military and had never wanted to become part of “Maliki’s militia.”

Not surprisingly, when this force came under tremendous stress, it fractured. As noted above, it is now being rebuilt, but not as a national army: as a Shia militia. And the U.S. should only be providing it with aid if we are given the right and the ability to turn it back into an apolitical, national army.