During the offensive by Islamic State militants that began in early June 2014, the group parlayed tactical advantages into significant territorial gains. Its use of multidirectional, vehicle-borne assaults made it seem as though Islamic State fighters were ubiquitous. The speed of these attacks threw Iraqi security forces (ISF) on their heels and allowed the militant group to capture land and weapons as state security forces withdrew. The Islamic State also succeeded in slowing the organization of an ISF counteroffensive by planting improvised explosive devices (IEDs) along roads and in houses. While these tactical successes have been discussed extensively by a number of Iraq analysts, the broader geopolitical context in which they took place requires further analysis.
The Islamic State’s military achievements have taken place largely along two preexisting, culturally defined fault lines. The first is between the primarily Shia Iraqi security forces and the Sunni majority areas where these forces are now operating in western Iraq. The second is the zone between the central government in Baghdad and the Kurdistan Regional Government (KRG) in Erbil that demarcates disputed territories between the two levels of government.
By exploiting gaps in the positioning of security personnel resulting from these twin domestic conflicts, the Islamic State has been able to make significant territorial gains. One consequence of Iraq’s internal divisions is that the Islamic State is not fighting a unified, strong, Iraqi army. Instead, an assortment of localized security forces—including well-trained Peshmerga in the Kurdish region, increasingly powerful Shia militias organized under the al-Hashd al-Shabi (popular mobilization) forces in central Iraq, and Sunni tribal protection forces scattered throughout the country—have taken control of security arrangements at a localized level. This fracturing of the national defense posture as a result of political disputes helps explain the Islamic State’s rapid expansion.
Iraq’s Sunni community has largely been left out of the political and security decision-making process in post-Saddam Iraq. Iraq’s Sunni heartland, principally in Anbar but with large populations in Salahaddin, Diyala, and Ninewa provinces, has struggled to develop effective, locally-staffed security institutions. One reason for this is a hesitance on the part of the federal government to provide arms or funding for Sunni tribes that could be used to oppose the state.
Though these areas are unquestionably part of federal Iraq, their security arrangements have been a source of considerable tension. This is primarily due to the sectarian composition of the mainly Shia Iraqi national army and the increased power of Shia militias. Local Sunnis, many loath to support the draconian rule of militant groups, still see a threat in the armed forces ostensibly sent there to protect them. At the same time, the Iraqi chain of command has appeared to lack the motivation to assert military power in Sunni areas. Part of this is due to poor training, inadequate supplies, and weak leadership. However, the principle cause is the overtly sectarian nature of the Iraqi state and the Sunni’s diminished position within it.
In contrast to disputes between Erbil and Baghdad, the nature of Sunni disputes with the central government has not been defined by territorial ambition. While some in the Sunni community advocate for an autonomous region, the main concern is maintaining a force to protect Sunni areas from Islamic State fighters and Shia militias. The Islamic State has been able to capitalize on these localized disputes in Sunni areas and exploit the security weaknesses they engender.
Islamic State Operations in Sunni Areas
The Islamic State has exploited the fractious security relationship between the ISF and the Sunni population. The group’s initial conquest of Fallujah in January 2014 and subsequent success in taking Mosul five months later was in part a result of preexisting tensions in those areas. In some Sunni communities, Islamic State forces were able to bolster their ranks through the recruitment of local Sunnis. Part of this is likely a result of alliances based on expediency rather than ideological agreement.
In combination with local recruitment, the Islamic State graphically promoted the killing of Shia civilians, government employees, and anyone else opposed to the creation of a new caliphate. These terror tactics polarized the local security environment and caused further hesitation among the under resourced, poorly trained Iraqi army forces charged with halting the Islamic State’s advance. That advance took place in the mainly Sunni cities and towns on the banks of the Tigris and Euphrates rivers.
The Iraqi government’s ad hoc response to the Islamic State’s advances in Mosul and other Sunni areas helped the Islamic State gain momentum along the Euphrates and Tigris corridors. The time it took for Baghdad to mobilize a counteroffensive, combined with the extensive road infrastructure along the two rivers, allowed the Islamic State to bolster their local positions rather than be content with hit-and-run attacks reminiscent of al-Qa`ida in Iraq (AQI).
The movements of Islamic State forces in the Sunni heartland did not take place in a vacuum. During the campaign to take Mosul, the Islamic State simultaneously undertook targeted operations in the territories that Baghdad and the KRG were fighting over. In part, this move was a consequence of circumstance due to the generally inchoate nature of the preexisting security arrangements in the disputed territories. It was also a tactical move meant to distract the Iraqi army, Shia militias, and Kurdish Peshmerga from mounting a serious, coordinated defense of Mosul.
In one particularly destructive attack, the Islamic State targeted the Kurdish Patriotic Union of Kurdistan (PUK) office in the contested city of Jalula on June 8, 2014 with a car bomb, killing 18 Kurdish Peshmerga. These types of attacks forced state security forces to focus attention on multiple fronts despite being ill prepared for the one evolving in the west of the country.
Baghdad, Erbil and the Disputed Territories
As the Islamic State’s forces pushed into the predominantly Sunni areas of western Iraq, they also expanded eastward into the disputed zone between the semi-autonomous Kurdish region to the north and federal Iraq to the south identified in Article 140 of the Iraqi constitution.
The disputed territories fall principally within four governorates: Ninewa, Erbil, Kirkuk, and Diyala. These territories form an arc stretching from northeastern Diyala province on the border with Iran to northwestern Ninewa province on the border with Syria. The contested status of areas within this belt is largely a legacy of former President Saddam Hussein’s Arabization policies. During the parliamentary discussions of the 2005 draft constitution, all sides agreed to postpone a decision on the disputed territories, especially oil-rich Kirkuk. Instead, they adopted Article 140 as the principle legislative mechanism through which the issue would be settled. The text outlines a series of steps to be taken, including public referendums in each of the disputed territories.
This status quo held even as implementation of Article 140 was postponed initially on December 31, 2007 and then effectively shelved. The arrangement worked for Erbil and Baghdad because both sides could say publicly that they were in control and neither had to make the politically difficult move of ceding territory.
Tensions increased somewhat during the government led by Nouri al-Maliki, especially after he deployed forces to the border between Salahaddin and Kirkuk in a bid to deter the Kurdish Peshmerga from occupying more territory south of Kirkuk City.
Even during this period of heightened tension, the status quo was effectively maintained. Kurdish Peshmerga and Iraqi security forces even jointly exercised control in parts of the contested districts through a combined security mechanism.
Islamic State in the Disputed Territories
Beginning in June 2014, the Islamic State was able to exploit gaps in the security cordon in the disputed territories to devastating effect. In these areas, neither the Iraqi army nor Kurdish Peshmerga had solidified their positions and instead relied on a disjointed, but stable arrangement of mixed administrative and territorial control that had developed since 2003.
The Islamic State was able to expand its influence in this environment as the governments in Erbil and Baghdad struggled to craft a coherent response. Tactically, Islamic State operations in the disputed territories allowed the group to draw ISF and Peshmerga attention away from the critical task of retaking Mosul and other areas in the country’s western region.
The extent to which local security forces—Kurdish and Arab alike—were ill prepared for the Islamic State’s actions in the disputed territories can be seen in events that played out in northern Diyala. On June 13, 2014, Islamic State forces entered the disputed towns of Jalula and Sadiyah, approximately 80 kilometers northeast and 60 kilometers north of Baghdad, respectively.
These towns, though formally part of Diyala province, are each home to mixed Kurdish, Arab, and Turkmen populations. In what would become a frequent strategy employed by the Islamic State, the group mounted sustained sorties in the countryside around Jalula and Sadiyah prior to launching a full attack on the cities directly.
The territorial acquisitions were an extension of previous military victories by the Islamic State in Suliman Beg, Amerli, and Hawija. It took nearly five months for a combined force of Iraqi army, Shia militias, and Kurdish Peshmerga to retake Jalula and Sadiyah.
A similar demonstration of the Islamic State’s exploitation of security weaknesses within the disputed territories took place in early August 2014 in the Ninewa town of Sinjar. The assault on Sinjar was combined with a string of attacks on Peshmerga forces in Gwer, Makhmour, Tal Keif, Qaraqosh, and Bartella.
The closest of these, Gwer, is roughly 25 kilometers from the Kurdish capital in Erbil. The scale of the Islamic State attacks, their speed, and their scope forced a rapid change in the Peshmerga force posture. Consolidating their defensive position to protect Erbil province, the Kurds were initially ill prepared to expand their security cordon in order to mount a sustained defense of Sinjar.
The Kurds had long maintained administrative and security control of the area, and the Iraqi army had positioned itself too far south on the Ninewa plain to be of assistance. Even if it had been close by, consistent threats to Ramadi and areas much closer to Baghdad in the Sunni heartland would have likely continued to draw Baghdad’s attention to the nearer threat. As the Islamic State was eventually pushed back from Erbil the group had consolidated around Sinjar, taking the city and forcing many of its Yazidi inhabitants to look for shelter on the slopes of nearby Mt. Sinjar.
One of the disputed areas where Kurdish forces have had notable success is in oil-rich Kirkuk province. Islamic State forces launched a series of raids near Kirkuk in early June 2014 prompting Kurdish forces to rapidly expand their line of control south to cover the entire province. This shift south drew a significant number of the Peshmerga force away from the frontlines in Ninewa and Diyala provinces. Iraqi army forces positioned in Kirkuk as part of the joint Arab-Kurdish units fled south toward Baghdad, again illustrating the poor security coordination in the disputed territories.
In contrast to Islamic State operations in the Sunni heartland to the southwest or in the disputed territories to the north and east, the militant group appeared content to harass Kirkuk City with insurgent-style attacks and bombings from its positions in nearby Hawija.
By concentrating its forces on consolidating territorial gains in other areas, particularly recently retaken Ramadi, the Islamic State can continue to utilize its Hawija position as well as its forces throughout the disputed territories to harass Kirkuk and draw the attention of Kurdish Peshmerga away from the group’s positions elsewhere.
Difficult Days Ahead
The Islamic State has proven adept at mounting rapid attacks across multiple geographic locations simultaneously. This has allowed the group to control huge swaths of Iraq. While a number of factors have contributed to its military success, Iraq’s internal divisions have been crucial.
Disputes between the central government and Iraq’s Sunni community regarding the composition of security forces and the division of political power have contributed to significant security gaps in western and northern Iraq. At the same time, the continued failure of Baghdad and Erbil to agree on a final status of the disputed territories has fostered the development of vulnerabilities in the local security structure.
The Islamic State’s military strategy has parlayed these internal divisions to expand its presence in the country. Its rapid, multi-pronged attacks against a variety of targets are well suited for success against the largely uncoordinated response of the Iraqi army, Shia militias, and Kurdish Peshmerga. Though some successes have been seen, the underlying disputes remain unaddressed and will need to be dealt with if Iraqi and other forces are to have any chance of decisively defeating the Islamic State.
Andrew Watkins is an energy and security analyst with the Iraq Oil Report. Mr. Watkins has spent more than four years living in and writing about Iraq.
The views expressed here are those of the author and do not reflect those of the Iraq Oil Report.
 Sam Jones, “Iraq crisis: sophisticated tactics key to Isis strength,” Financial Times, June 26, 2014.
 Alice Fordham, “Ambushes, Mines, and Booby Traps: Islamic State Militants Change Tack,” NPR, October 21, 2014.
 The House Armed Services Committee in the 2016 National Defense Authorization Act sought to allocate one-quarter of the proposed $715 million earmarked for Iraq military support to go directly to the Kurdish Peshmerga and Sunni militias. Julian Pecquet, “Defense bill recognizes Iraq’s Kurdish, Sunni militias as a country,” Al Monitor, April 27, 2015.
 Stephen Wicken, “Iraq’s Sunnis in Crisis,” The Institute for the Study of War, May 2013.
 Dexter Filkins, “The Real Problem In Iraq,” The New Yorker, May 19, 2015.
 Jim Muir, “Fears of Shia muscle in Iraq’s Sunni heartland,” BBC News, May 18, 2015.
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 Joost Hiltermann, Sean Kane, Raad Alkadiri, “Iraq’s Federalism Quandary,” The International Crisis Group, February 28, 2012, pp. 3-4.
 Mohammed Tawfeeq and Chelsea J. Carter, “Officials: Islamic State recruiting on the rise in Sunni areas of Iraq,” CNN, August 11, 2014.
 Alice Fordham, “The Other Battle In Iraq: Winning Over Sunni Muslims,” NPR, February 3, 2015.
 For an updated map of territorial control in Iraq see: “Iraq and Syria: ISIL’s Reduced Operating Areas as of April 2015,” The United States Department of Defense, April, 2015.
 Full Arabic text of Iraq’s constitution with English translation by Zaid Al-Ali, “Iraq’s final constitution (English),” 2006.
 Sean Kane, “Iraq’s Disputed Territories: A View of The Political Horizon and Implications for U.S. Policy,” The United States Institute of Peace, 2011, p. 12.
 John Fawcett and Victor Tanner, “The Internally Displaced People of Iraq,” The Brookings Institution-SAIS Project on Internal Displacement, October 2002, p. 11.
 Steven Lee Meyers, “Politics Delay and Iraqi Census,” The New York Times, December 6, 2010.
 Karim Abed Zayer, “Maliki Deploys ‘Tigris Force’ to Kirkuk,” Al Monitor, November 13, 2012.
 Joint Peshmerga-ISF positions in the disputed territories were initially part of the U.S.-administered Combined Security Mechanism (CSM). Larry Hanauer, Jeffery Martin, and Omar al-Shahery, “Managing Arab-Kurd Tensions in Northern Iraq After the Withdrawal of U.S. Troops,” RAND, 2011. pp. 2-3.
 Harvey Morris, “Islamic State occupation puts territorial dispute into perspective,” Rudaw, April 11, 2014.
 Greg Botelho and Jim Acosta, “U.S. official: Mosul invasion ‘might be some time from now,’” CNN, April 9, 2015.
 “In Iraq, Islamic militants continue drive, grab 2 towns near Baghdad,” CBS News, June 13, 2014.
 “Control of Terrain in Iraq,” The Institute for the Study of War Blog, June 19, 2015.
 Saif Hameed, “Iraqi forces say retake two towns from Islamic State,” Reuters, November 23, 2014.
 Dexter Filkins, “The Fight of Their Lives,” The New Yorker, September 29, 2014.
 Mohammed A. Salih and Wladimir van Wilgenburg, “Iraqi Yazidis: ‘If we move they will kill us,’” Al Jazeera, August 5, 2014.
 “Iraqi Kurds ‘fully control Kirkuk’ as army flees,” BBC News, June 12, 2014.