Since the start of the war in Iran, the United States and Israel have launched successive attacks on Iran-allied armed groups in Iraq. The strikes have caught many observers by surprise, as previous U.S. attacks on Iran-backed groups have been mostly retaliatory, responding to specific provocations. Up until Tehran and Washington reached a cease-fire on April 7, the United States seemed to be hitting Iran’s whole network in Iraq, regardless of whether groups had directly attacked U.S. assets.

Their targets have included key groups such as Kataib Hezbollah, Harakat al-Nujaba, and Kataib Sayyid al-Shuhada, which recently hit military bases hosting U.S. troops in Jordan, Kuwait, and Iraq; and groups not claiming credit for attacks, including Harakat Ansar Allah al-Awfiya. Other targets have been accused of oilsmuggling, including Asaib Ahl al-Haq, or are immersed in the Iraqi economy and close to Hezbollah in Lebanon, such as Kataib al-Imam Ali. The United States has designated all six of these groups as terrorist organizations.

Since the start of the war in Iran, the United States and Israel have launched successive attacks on Iran-allied armed groups in Iraq. The strikes have caught many observers by surprise, as previous U.S. attacks on Iran-backed groups have been mostly retaliatory, responding to specific provocations. Up until Tehran and Washington reached a cease-fire on April 7, the United States seemed to be hitting Iran’s whole network in Iraq, regardless of whether groups had directly attacked U.S. assets.

Their targets have included key groups such as Kataib Hezbollah, Harakat al-Nujaba, and Kataib Sayyid al-Shuhada, which recently hit military bases hosting U.S. troops in Jordan, Kuwait, and Iraq; and groups not claiming credit for attacks, including Harakat Ansar Allah al-Awfiya. Other targets have been accused of oilsmuggling, including Asaib Ahl al-Haq, or are immersed in the Iraqi economy and close to Hezbollah in Lebanon, such as Kataib al-Imam Ali. The United States has designated all six of these groups as terrorist organizations.

The purpose of the U.S.-led strikes is to decapitate the leadership and dismantle the infrastructure of Iran’s allied networks in Iraq. After a possible cease-fire with Iran, the United States is likely to sustain pressure on the groups by pushing Iraq to disarm them and even restructure the umbrella organization that oversees them, the Popular Mobilization Forces (PMF).

Iran-backed groups in Iraq established the PMF in 2014 to mobilize against the Islamic State. In 2016, the Iraqi parliament passed a law incorporating the organization into the country’s security architecture. Kataib Hezbollah, the largest Iran-backed group in the PMF, has been responsible for leading and executing numerous attacks on U.S. and coalition troops in Iraq and in neighboring countries such as Syria and Jordan.

The United States has not designated the PMF as a terrorist organization, but it has sanctioned top PMF leaders and what the United States calls the PMF’s corporate arm, the Muhandis General Co. Last year, Washington successfully pressured the Iraqi parliament into withdrawing a controversial bill that would have empowered the PMF further, the Nationalreported in August. In hindsight, all of these actions appear to have been precursors to the United States’ indiscriminate air campaign targeting pro-Iran groups.

Decapitation by air power and prospective disarmament efforts by the Iraqi government may weaken Iran-linked groups, but they are unlikely to destroy them completely. There are two interconnected reasons why.

First, the militias are supported by tribal networks in Iraq’s Shiite-majority and oil-rich central and south regions. Second, the Iraqi parliament today broadly supports Iran-backed groups. Around 80 to 90 legislators belong to pro-Iran armed parties in Iraq, and they rely on tribal loyalty to stay in office. Armed pro-Iran parties, led by Asaib Ahl al-Haq, the Badr Organization, Kataib Hezbollah, and others, can mobilize more than one-third of parliament to block the body from reaching a quorum. There are 329 seats in Iraq’s parliament.

The leaders and rank-and-file militants of Iran-allied groups belong to tribal networks in provinces such as Basra, Dhi Qar, Maysan, and Muthanna, which are typically heavily armed and possess extensive weaponry. They also make up the fabric of Iraq’s security forces and provincial institutions. When a high-level official belongs to a prominent tribe, these networks can wield influence in top government bodies.

Tribes from these central and southern regions mobilized in the Iraqi government’s war against the Islamic State in 2014, further empowering them. Iran-backed groups in the PMF relied on volunteering tribesmen to form brigades on government payroll. The tribesmen who contributed to battle at that time were also ones who voted for the armed parties that have gained seats in parliament since 2018.

When the war against the Islamic State officially ended in Iraq in 2017, small and medium arms proliferated throughout the country, especially in the south. The country was also increasingly affected by climate change, leading tribes to engage in internecine conflicts over land and shared water resources, among other issues. As consecutive Iraqi governments struggled to stop those disputes, local sheikhs became more involved.

Even if the United States and Israel assassinate proxy groups’ top and middle-rank leaders, those groups would fragment, and thousands of affiliates would find shelter among their tribesmen, making it difficult for the government and judiciary to hold them accountable. Armed tribesmen could violently confront Iraqi security forces tasked with capturing wanted militiamen. Such risks also exist near major oil-producing fields in Iraq’s southern provinces, where tribesmen have the capabilities to disrupt operations if they decide to assert their power against the state.

Militias could regroup and produce new armed proxies, too. Some of Iraq’s southern provinces border Iran, with a few of the same tribes residing in both countries. It is easy for members of these groups to cross porous land boundaries, shelter people when needed, and smuggle weapons and commodities.

Iran understands the strategic importance of tribes in sustaining its proxies, and its militias actively engage sheiks in their events. Harakat al-Nujaba, one of the fiercest anti-U.S. groups in Iraq backed by Iran, held its first annual so-called tribal support conference in Baghdad in February, bringing together tribal leaders with the militant group.

The intertwined relationship between the Iran-backed groups and tribal networks is bolstered by ties between tribal networks and Shiite political parties, several of which are linked to Iran-backed groups. Sheikhs and their followers may vote for those parties due to kinship and a shared opposition to the United States and Israel but also because those political parties offer tribal leaders and voters key material incentives.

Tribes have been involved in Iraq’s political system since the state’s founding—and in fact, before, as British colonial policies contributed to entrenching Iraqi tribes. More than one-third of the 1928 assembly’s members were sheikhs, historian Adeed Dawisha writes in Iraq: A Political History. Consecutive Iraqi governments have varyingly placated tribes by distributing jobs or land, using these measures to consolidate social control and earn political support. Saddam Hussein even recruited personnel from specific Sunni tribes for security positions.

Sheikhs no longer hold the lion’s share of seats in Iraq’s parliament, but their interests remain salient, in part because of their power to mobilize votes. In some provinces, such as Anbar, Basra, Dhi Qar, and Diyala, for example, tribal networks have influence over provincial politics; in other cases, sheikhs run companies that cooperate and compete with party-linked companies for key contracts. Overall, armed groups benefit from befriending financially and politically powerful sheikhs.

If Washington succeeds in pushing the next Iraqi government to dismantle some Iran-backed militias and hold their leadership accountable for attacks, just as it pressured parliament to withdraw the PMF bill last year, Baghdad will need to carefully consider how it would deal with uncooperative tribes sheltering wanted militiamen or those that rebel by blocking roads or shutting down oil fields.

It would be impossible for Iraq to disarm Iran-backed militias safely without weakening the tribal networks behind them. Not only does the state lack the coercive capacity to fully disarm some tribes—but at least for now, no Iraqi government can afford the social and political costs of doing so.