As coalition forces arrived in Baghdad at the start of March 2003, the city descended into chaos. Crowds surged into the streets to celebrate the fall of Saddam Hussein, to destroy his regime’s most potent symbols, and to take revenge on those who had sustained his rule. Murals of Saddam were defaced, his iconic statue in Firdos Square was pulled down, and Baath Party functionaries were hunted by their former charges.

Yet the appearance of anarchy created by the wave of thefts, kidnappings, and murders that swept the city obscured the deliberate, directed actions of more coherent forces. Beneath the cover of chaos, numerous groups were maneuvering into position to pursue their agendas on the uncertain terrain of post-Saddam Baghdad.

As remains the case to the present day, the post-Saddam power vacuum created opportunities for ambitious, radical, and determined political factions. At the onset of the occupation, one such group emerged unexpectedly on Baghdad’s periphery. In what was then known as Saddam City, the Iraqi capital’s largest and most notorious ghetto, former associates and devotees of the martyred Shia cleric Grand Ayatollah Sayyid Mohammad Mohammad Sadiq al-Sadr­ took to the streets to provide services such as trash collection, traffic control, and food distribution. The group—which became known as the Sadrists—networked through the religious institutions scattered among the area’s estimated two million residents and, within a few short weeks, had revived elements of the late cleric’s organization and begun the process of rekindling the mass movement that he had founded prior to his assassination, in 1999. Capitalizing on the still-potent force of Sadr’s legacy among the city’s Shia underclass, as well as the power vacuum created by the sudden and complete disintegration of the government, the Sadrists renamed the slum Sadr City and began expanding their power around the capital’s impoverished, sprawling margins.

Although the instability of the invasion’s early days enabled the Sadrists to generate vital initial momentum, their rise proved as unwelcome as it had been unexpected. Core elements of the Sadrists’ agenda (and of the manner in which they would pursue it) resulted in a cold reception by the dominant players of the nascent post-Saddam order. Their outspoken and uncompromising belligerence toward the United States­­–led coalition won them the enduring enmity of U.S. commanders. The martyred Sadr’s legacy of virulent hostility toward leading Shia figures, families, and factions (many of whom secured positions of power in the emerging political order by cooperating with the occupying powers) ensured the Sadrists’ ostracism from the corridors of power. Lastly, Sadrists would have to navigate the divisions and prejudices of Iraqi society. Their rise as a movement of the downtrodden Shia underclass, with ambitions not only to empower their demographic base but also to exact vengeance upon those who had oppressed, neglected, and humiliated them in decades past, meant that they would be viewed with hostility and suspicion by many—not least by their “betters” within Iraq’s Shia community.

The militia had grown massively, but it had become all the more controversial and structurally incoherent.

Nonetheless, the Sadrists would become a pivotally influential force in Iraq. They faced an array of formidable obstacles from the outset (and they would thereafter acquire additional, powerful foes—al Qaeda foremost among them), but the Sadrists possessed a rare and valuable commodity that would fuel their ascent: the ideological bond that the martyred cleric had forged among the masses of Iraq’s Shia underclass during the 1990s. On a national landscape where the populace had been systematically atomized and depoliticized over a period of decades, the Sadrists’ opportunity to build from a genuine grassroots base was an extraordinary asset. With Mohammed Mohammed Sadiq al-Sadr’s only surviving son, Muqtada al-Sadr, at the helm of the movement’s resurgence, and the Mehdi Army militia as its principal organizational body, the Sadrists’ ability to mobilize the Shia underclass would prove decisive in shaping the their fortunes.

THE SADRISTS’ FALTERING FIRST STEPS

The Sadrists’ first forays of the post-Saddam era were inauspicious. In their initial efforts to seize control of Iraq’s Shia clerical establishment in Najaf, they became embroiled in a controversial murder that cast their enterprise as lawless and prone to savage violence. On April 10, 2003 (only a day after the fall of Baghdad), the respected Shia cleric Abd al-Majid al-Khoei, son of the late Grand Ayatollah Abd al-Qasim al-Khoei, was attacked by Sadrist supporters within the confines of one of Najaf’s holiest sites and then brutally murdered.

Iraqi Shiite Muslim men from Hashid Shaabi (Popular Mobilization) hold portraits of (front to back) Iran's late leader Ayatollah Ruhollah Khomeini, Iraq's late Shi'ite cleric Mohammed Baqir al-Sadr, and Supreme Leader Ayatollah Ali Khamenei during a parade marking the annual al-Quds Day, or Jerusalem Day, on the last Friday of the Muslim holy month of Ramadan in Baghdad, July 10, 2015. Thaier al-Sudani / Reuters In Baghdad, they fared little better. Pressure was mounting on the Sadrists in relation to the looting that was devastating the city. Fairly or not, the Shia underclass was blamed for a grossly disproportionate share of this looting, and the anger of many Baghdadis intensified, as the Sadrists were perceived to be maintaining control over the slums while allowing their supporters free rein to pillage the city center. Representatives of Iraq’s fledgling government encouraged Muqtada to condemn the looting and aid in the restoration of order, but he refused. Instead, he condoned the obliteration of the former status quo—provided that looters paid a religious tax to Sadrist clerics on the value of their booty. This provocation confirmed popular suspicion that the Shia poor had been the principal culprits in the looting (with the complicity of the Sadrists), and the backlash was such that it even prompted criticism from former associates and devotees of Muqtada’s father.

Through the months that followed, the Sadrists’ outspoken belligerence against the occupation and its Iraqi enablers did earn them significant international acclaim—particularly as popular discontent with foreign occupation mounted. Yet even this, their greatest early achievement, came with significant caveats. In immediate, practical terms, it led the Sadrists to a series of devastating defeats on the battlefield (most notably in Najaf during the summer of 2004). Less vividly, but no less influentially, it also further exacerbated their reputation for recklessness and strategic myopia.

The Sadrists thus cemented a reputation as aggressive outsiders during the initial phase of the post-Saddam era. In the political sphere, their relentless opposition to coalition forces, and to the parties of the Shia establishment that were cooperating with the occupation, assured their official marginalization. Likewise, their provocation of instability rendered them widely unpopular among the general population. Rather than softening their stance, however, the Sadrists embraced their outsider status—forming their own shadow government, growing increasingly militant in word and deed, and staking an outspoken claim as the leading Shia opponent of Iraq’s new political order.

THE ASCENT OF THE SADRISTS

The fate of the Mehdi Army is instructive as we seek to confront the violence that is wracking Iraq at present.

Sectarian violence—which began as an undercurrent within the Sunni insurgency, gained momentum during the spring and summer of 2004, and intensified dramatically in the context of the January 2005 elections—altered Iraq’s strategic landscape in several ways to the direct benefit of the Sadrists. Most critically, the rise of al Qaeda in Iraq and the ferocious sectarianism of Sunni jihadis compelled the Shia elite to put aside their feud with the Sadrists and reach out, however warily, in the name of sectarian solidarity.

The Sadrists’ rise continued apace with the escalation of sectarian violence through 2005 and into 2006. The scale of the killing and the resulting social polarization grew to such levels that observers labeled the conflict a civil war. As Shia neighborhoods in and around Baghdad were subjected to devastating mass-casualty attacks—and neither Iraqi nor American military forces proved able to secure the populace—the Mehdi Army emerged as Shia civilians’ indispensable bulwark against the Sunni jihad. Concurrently, in the political realm, the Sadrists’ inclusion within the ruling United Iraqi Alliance brought them heightened power, increased revenues, and enhanced respectability. The Sadrists and their militia thus rose to positions of previously unimaginable influence during a remarkably short period of time, with Muqtada being hailed as a kingmaker in the highest levels of Iraqi politics, and the Mehdi Army seizing control over vast tracts of central and southern Iraq.

Mehdi Army Women loyal to Shi'ite cleric Moqtada al-Sadr march during a parade in Najaf, June 21, 2014. Ahmad Mousa / Reuters

BETRAYAL, EXILE, AND DEFEAT

By late 2006, the Sadrists were a towering force in Iraq. Muqtada al-Sadr was an influential national figure, Sadrist politicians formed a central component of the Iraqi government, and the movement was the near-exclusive political vehicle for Iraq’s burgeoning Shia underclass. The Mehdi Army, meanwhile, was larger and more powerful than ever before. The militia had absorbed legions of new recruits, it controlled expansive terrain, and its fighters could claim significant credit for having turned the tide of the sectarian war. Furthermore, the demographic changes that had swept Baghdad augured well for the Sadrists’ future. Not only was the city more heavily Shia than at any time in its long history, but the movement’s underclass supporters had also grown as a percentage of that Shia majority, and expanded territorially as well.

Yet despite the Sadrists’ remarkable advances, they faced significant and growing problems. First, while the Sadrists’ rise to power had conferred a broad array of benefits, with power came increased responsibilities, heightened expectations, and intensified public scrutiny. Their successes brought added burdens that they struggled to manage. Second, the Mehdi Army’s ascendancy in Baghdad had been matched by both the intensification of its notoriety for brutal violence, as well as the exacerbation of its organizational problems. The militia had grown massively, but it had become all the more controversial and structurally incoherent. Third, impending Shia victory in the sectarian war meant that, in the eyes of Prime Minister Nuri al-Maliki and the dominant players of the Shia establishment, the Mehdi Army had served its purpose. The diminishing threat of al Qaeda and the Sunni insurgency meant the dissolution of the principal force that had bound the rival Shia factions together in the first place.

Mehdi Army fighters loyal to Shi'ite cleric Moqtada al-Sadr take part during a parade in Baghdad's Sadr city June 21, 2014. Ahmed Saad / Reuters Beset by a host of internal problems, and confronted by an array of external challenges, the Sadrists would experience a precipitous drop in their fortunes during 2007 and 2008. Unable to consolidate their hard-fought gains, the Sadrists found themselves betrayed by their Shia establishment rivals and exposed to a devastating American-led offensive in the context of the surge. Muqtada was driven into exile, Sadrist politicians became outsiders once again, and the Mehdi Army was routed to the point that Muqtada felt compelled to dissolve it entirely.

Contrary to the often-dire warnings of contemporary observers, the Mehdi Army was chased from the field without a large-scale eruption of violence. Instead, with the exception of fleeting turmoil in March 2008 and sporadic clashes with American and Iraqi forces in the months that followed, the militia appeared to implode. Not only was it driven from the territory that it had captured during the sectarian war but it was also forced to cede control over the heartland of the Sadrist movement. The scope of its defeats in Baghdad and southern Iraq were such that Muqtada ordered the wholesale dissolution of the once fearsome militia, leaving the future direction of the rekindled Sadrist movement in question.

Close study of the Mehdi Army’s campaign exposes how and why the militia imploded in the manner that it did. By mobilizing tens of thousands of young men, the Mehdi Army had become one of the most formidable forces in post-Saddam Iraq. However, despite the militia’s impressive growth, Sadrist leadership was unable to rally a cohesive, coherent, mass-based insurgency from among their demographic base. In examining the Mehdi Army’s fortunes at the local level, it is evident that this outcome was largely predetermined by the condition of Iraqi society. With Iraq’s Shia underclass having been ravaged and atomized by an array of historical forces (including factors as mundane as large-scale rural-to-urban migration and tribal fragmentation, and as exceptional as the predations of Baathist governance and the deprivations of United Nations-imposed sanctions during the 1990s), civil society was not merely infertile ground for the cultivation of popular insurgency but, in places, toxic. In keeping with the best practices of insurgent warfare, the Mehdi Army had grown by going local, and absorbing local segments of Iraqi society on a neighborhood-by-neighborhood basis. In so doing, it conquered broad swaths of Iraq. However, owing to the brutalized condition of Iraqi society and the particular qualities of those who came to dominate the militia’s ranks, this same process poisoned the Mehdi Army from within.

The fate of the Mehdi Army is instructive as we seek to confront the violence that is wracking Iraq at present: the persistent inability of Iraq’s post-Saddam governments to effectively secure and administer their country will continue to create opportunities for radical militant groups with alternative visions for Iraq’s future; but said militants will inevitably struggle to find sound footing on the degraded terrain of Iraqi society, and will remain vulnerable to the concerted application of force.

This article is excerpted and adapted from The Death of the Mehdi Army: The Rise, Fall, and Revival of Iraq's Most Powerful Militia (Hurst, 2015).