Iraq's Bekaa Valley

A battle is unfolding in Saddam Hussein's old tribal capital of Tikrit. Unthinkable just a decade ago, the main government forces leading the battle are Shiite fighters -- the Popular Mobilization Units (PMUs) that are under the control of militia leaders. These forces' main partners are Iran and Lebanese Hezbollah. U.S. Chairman of the Joint Chiefs of Staff General Martin Dempsey has called the situation "the most overt conduct of Iranian support" since the war against the Islamic State of Iraq and al-Sham (ISIS) began. But it doesn't have to be a bad thing, he hinted, as long as such forces refrain from inflaming sectarian tensions.

His comments get to the heart of the debate over Iran's role in Iraq and the appropriate division of labor between the U.S.-led international coalition and Tehran in the fight against ISIS. The White House seems to view growing Iranian involvement in the war as a reality that cannot be wished away, which is probably true, but also as a step forward in U.S.-Iranian relations, which is arguably naive.

Events on the ground in eastern Iraq suggest a different way of looking at the issue. If anything, the battle for Tikrit has shown that there is a whole side of the war from which the international community has been deliberately excluded. Iran and its Iraqi proxies have been carving out a zone of influence in eastern Iraq for well over a decade. And this zone, as Dempsey noted, is expanding.

Iraq, in short, could be experiencing what Lebanon did decades ago as Hezbollah fighters took the Bekaa Valley. In this case, the land in question is Mesopotamia and the forces are PMUs, but the result will be the same: a swath of land in which the government is gradually ceding ground to powerful paramilitary factions with strong terrorist connections.

BADLANDS

There is a natural blending of Iraq and Iran in their shared border provinces. Large Shiite populations extend northeast from Baghdad to Iran along the Diyala River Valley. To the southeast are the largely Shiite border provinces of Wasit and Maysan, where the border with Iran dissolves into ungovernable marshes. Trade, smuggling, and religious pilgrimages along age-old crossing points and rivers permanently link these places. But since 2003 Iran has gone beyond these traditional ties by enmeshing the border provinces through subsidizing shared electricity grids, medical services, and refined oil products.

Eastern Iraq has also been a literal and figurative battlefield between Iranian-backed Iraqi militants and the Iraqi state. Ravaged by the Iran-Iraq War, the borderlands soon after the cease-fire became sites of tit-for-tat border raids. Baghdad sent in the Mujahadeen-e-Khalq (MeK), Shiite opponents of the Iranian theocracy classified as a terrorist organization by the United States. Tehran sent in the Badr Corps, an Iraqi Shiite force recruited by Iran. In the 1990s, Iran also periodically sent its air force into Iraq to hit the MeK. It even fired salvos of Scud-like missiles into Diyala as late as 2001.

Indeed, one of the least recognized facts about the fall of the Saddam government in 2003 was that two invasions took place: one from the south by the U.S.-led coalition and another from Iran, down the Diyala River Valley, by Iranian-backed Badr columns. During the Iran-Iraq War, the Badr Corps had fought as a 10,000-strong division alongside the Iranian military against Saddam's government; they did it again in 2003.

Cross-sectarian Diyala holds a special place in the hearts of the Iranian-backed militia leaders in Iraq. The leader of the Badr Corps, Hadi al-Amiri, is a native of Diyala, born in Khalis, where the Diyala River Valley and the Baghdad-Kirkuk road converge in the south of the province. Working with the U.S.-led occupation forces after Saddam's regime fell, Amiri ensured that the Fifth Iraqi Army Division, headquartered and recruited in Diyala, was packed with Badr officers.

The Badr Corps also made sure to pay back their bitter adversaries, the MeK. Camp Ashraf, the MeK cantonment, was just 25 miles north of Khalis on the Baghdad-Kirkuk road. After the area was handed over from the United States to the Fifth Division in 2009, Camp Ashraf began to suffer repeated deadly attacks. Shiite militia gunmen periodically overran the camp; in one attack in April 2011, militants killed 36 and wounded 320. Eventually, the MeK and their families were removed to Baghdad. Amiri now operates Camp Ashraf as his security headquarters.

As Iraq descended into fighting last summer, the Badr Corps expanded their control, spreading north to Kirkuk, east to the Lake Hamrin area, and west to Tikrit. The PMUs in Diyala have a strong connection to the group, either because Badr members directly answered the government's calls in early summer 2014 for popular mobilization or because PMU subgroups such as Kataib Hezbollah are led by Badr commanders such as Abu Mahdi al-Muhandis.

In June 2014, Iran and the Badr Corps opened a direct line of supply between Iran's arms depots and the Badr bases, using the Parwezkhan border crossing in northern Diyala. Even now, the bases get daily shipments of Iranian rocket ammunition for PMU artillery units. Iranian drones and other air support have become a regular sight over Diyala. And PMU headquarters have special intelligence and air support cells manned by Iranian Revolutionary Guard or Lebanese Hezbollah operators -- exactly the roles Americans played before 2011.

The PMUs in Diyala have also been associated with some of the most significant atrocities committed by pro-government forces: the August 22, 2014, massacre of 34 Sunni civilians at the Musab bin Omair Mosque in Imam Wais and the January 26, 2015, killing of at least 72 Sunni men and boys in Barwana. In the Shiite Turkmen areas along the Baghdad-Kirkuk road, the PMUs have actively prevented the return of Sunni civilians into formerly mixed areas.

BADR POWER

Badr Corps-aligned PMUs and the Badr-led Fifth Iraqi Army Division are now the dominant armed forces throughout the Diyala River Valley and all the way from the southern outskirts of Kirkuk down to northern Baghdad, an area of nearly 5,000 square miles. This canton includes most of the lands that have been recaptured from ISIS, and it is quickly expanding westward to the Tigris River.  

The PMUs will probably eventually seek to play a role in all of Iraq's major battlefields, including Mosul. It remains to be seen whether they will be willing to work alongside the U.S.-led coalition or seek to supplant Western assistance in future operations, as occurred in Tikrit.

In addition to displacing the United States, Badr-linked PMUs are taking the place of regular Iraqi security forces in central Iraq. Iran has always sought to dominate cross-border trade and profit from the multibillion-dollar pilgrim business: in November 2014, the PMUs went further by taking a leading role in the protection of the Ashura pilgrimage. PMUs fought their way into the town of Jurf al-Sakr, an ISIS stronghold on the route between Baghdad and the shrine city of Karbala.

The PMUs have also been pushing into the border of Iraqi Kurdistan, resulting in numerous armed clashes, and have become the dominant security force in the capital as the battle against ISIS drew Iraqi Army units north and west into Anbar. And in critical economic hubs such as Basra, there has been an almost complete absence of Iraqi Army forces for nearly a year. Replacement units face resistance from powerful Shiite militias that have prowled Basra's Sunni areas, doling out payback for Islamic State attacks farther north.

CAREFUL WHAT YOU WISH FOR

Significant controversy will continue to surround the issue of the PMUs in Iraq. To the Shiite population, the popular mobilization is inspiring -- a counter to the humiliating collapse of the Iraqi military and a sign that Iraqis are individually more willing and able to defend themselves than their government was.

Iraqi leaders will continue to argue that the PMUs are essential to the counteroffensive against ISIS and that it is too early in the conflict to try to restrain them. Iraqis will also contend that criticism of PMU leadership for their involvement in terrorist attacks on U.S. and British troops and civilians is hypocritical. After all, the Western powers seem perpetually eager to work with the Sunni tribes that also attacked them from 2003 onward.

Shiite Iraqis will further argue that finger-pointing at Iran is off base. Iran stepped up while the United States dithered, they claim with some justification, although it might be added that Iran did not deliver the removal of Prime Minister Nouri al-Maliki, nor does its help come free of charge -- the costs are just hard to see right now.

Iraqi leaders privately admit that although the PMUs represent an unsettling expansion of the power of Iranian-backed militia leaders, they can be contained. In recent weeks, the Shiite religious leadership has begun to clarify the need to fold the PMUs into the national defense structure and end their sectarian atrocities. We can handle them, Iraqi leaders say, but for now the PMUs are needed.

This final claim is the most open to question. After Tikrit, the PMUs might have run out of road, and any attempt to play them into the Sunni redoubts of Mosul or Anbar could prove counterproductive. Further, the PMUs might very well not be controllable, much as Lebanese Hezbollah did not simply disarm after Israel withdrew from Lebanon. Hezbollah came to dominate the country, and now its soldiers are fighting in Syria and Iraq.

Neither the United States nor Iraqi leaders should harbor any delusions about the potential danger posed by the PMUs. These groups embody the classic civil-military security dilemma: the armed force that is best able to protect a country from external enemies is also the greatest potential risk to the civilian leadership.

Perhaps the most striking difference between the risks of Hezbollah rule in Lebanon and PMU rule in Iraq is scale. Lebanon has 4.5 million citizens and no major resources to speak of. Iraq has a population of 36 million and likely boasts hydrocarbon reserves comparable to those of Saudi Arabia. The world cannot afford to lose Iraq to a fate such as Lebanon's.

Michael Knights, a Lafer Fellow with The Washington Institute, has worked in all of Iraq's provinces, including periods spent embedded with the Iraqi security forces. His latest study is the Institute report The Long Haul: Rebooting U.S. Security Cooperation in Iraq.

This article originally appeared on the Foreign Affairs website with the title "After Tikrit."