Iraq’s Contested Sovereignty After the U.S. Military Withdrawal

On September 30, 2026, the last U.S.-led coalition troops departed Erbil air base in northern Iraq, ending the latest chapter of a military presence in the country that began with the 2003 invasion, briefly ended in 2011, and resumed in 2014 to fight the Islamic State. Baghdad celebrated, Washington claimed victory, and Iran-aligned factions rejoiced. In the Kurdistan Region, the response was alarm.

Each reaction reflects a different calculation on what Iraq becomes without the United States as referee, target, and security backstop. The withdrawal resolves one longstanding dispute over Iraqi sovereignty while bringing another to the fore: the gap between the state’s formal monopoly on force and its ability to exercise it. That question becomes more urgent eight months into the U.S.-Israeli war on Iran, which has repeatedly entangled Iraq, especially the Kurdistan Region in a regional conflict, all while Prime Minister Ali al-Zaidi seeks to bring armed groups under state control by June 30, 2027, which is a postponed date that was originally slated to coincide with the U.S. withdrawal.

From Withdrawal to Sovereignty

The departure followed a two-phase plan agreed to in 2024 by the Biden administration and then-Prime Minister Mohammed Shia al-Sudani, which President Trump held to as part of his pledge to end an “endless war.” By January 2026, coalition advisers had left federal Iraq, with troops remaining in Erbil to support operations in Syria. Despite the U.S. launching the war against Iran on February 28, al-Zaidi confirmed in July that the remaining U.S. troops would leave by the end of September.

Their departure removed a roughly 1,500-strong military footprint and the air defenses that accompanied it, although training and intelligence cooperation will continue. Baghdad marked the occasion with four “Sovereignty Days” of national holiday, underscoring its claim that the state, not foreign armies or factions, decides on issues of war and peace. At the UN General Assembly, al-Zaidi pledged that weapons would remain with constitutional institutions and that Iraq’s relationships with Western states would shift from military to economic cooperation.

But the sovereignty narrative is more than symbolism. It is also central to al-Zaidi’s strategy for confronting the armed factions, which have long justified maintaining their arsenals by pointing to the U.S. presence. As former U.S. ambassador Douglas Silliman put it, the prime minister is building a case that those groups no longer need their weapons.

Some factions appear willing to accept that logic. Saraya al-Salam was formally integrated in June, while Asaib Ahl al-Haq and Kataib al-Imam Ali have reached understandings with the government. Badr leader Hadi al-Amiri accepted state control of weapons in principle, but he has ruled out any confrontation with “the resistance.”

Others remain defiant. Kataib Hezbollah leader Abu Hussein al-Hamidawi declared that “the resistance has won this round” and suspended operations, except against “hostile aircraft,” until the state has air defenses. He has denied reaching any disarmament deal with al-Zaidi, while Kataib Hezbollah and Harakat al-Njuaba continue to refuse to surrender their “resistance weapons. In principle, Al-Hamidawi accepted that decisions over war and peace should be “one, or at least agreed upon,” while in practice seeking to continue the status quo:  refusing disarmament to ensure no state monopoly over the use of force. Iran’s Revolutionary Guards, meanwhile, hailed an “historic victory.”

The withdrawal therefore weakens the factions’ principal political justification without eliminating their military capabilities or their ability to assert them. For now, they reportedly remain on a war footing alongside the IRGC, although both the U.S. and Iran-aligned militias have given assurances to the prime minister to refrain from attacking each other for 90 days after the withdrawal, to keep the situation from deteriorating in the near term. While this buys time, it does not resolve the issue.

The Security Gap

The Kurdistan Region challenges the other side of Baghdad’s sovereignty claim. If the federal government insists that security and the use of force belong exclusively to the state, it must also demonstrate that it can protect the territory and populations under its authority. The Kurds—alongside Sunnis and other Shia political parties not associated with Iran—are questioning the state’s ability to do this.

No part of Iraq has felt the consequences of the coalition’s departure more immediately than the Kurdistan region. Since late February, it has been hit by more than 1,000 drone and missile strikes. U.S. Patriot and C-RAM systems based in Erbil intercepted many of them. Those systems are now gone.

KRG Prime Minister Masrour Barzani told the Financial Times that leaving the region undefended was “shameful,” and prominent Kurdish figure Masoud Barzani warned of a security vacuum reminiscent of the conditions that preceded the Islamic State’s rise after the 2011 U.S. withdrawal.

Structurally, Erbil cannot run air defenses alone, since Iraqi airspace is a federal responsibility. At the same time, the U.S. partnership that long served as a hedge against Baghdad has disappeared, while coalition financial support for the Peshmerga—the internal security forces of the KRG—has ended.

As a result, Erbil is in a difficult position, with the U.S. withdrawal potentially strengthening the authority of the central government while making the KRG more dependent on the Iraqi state for its security. Erbil has responded by completing the merger of rival Kurdistan Democratic Party and Patriotic Union of Kurdistan forces and pressing Baghdad to address longstanding grievances, from Peshmerga salaries that are less than half of Iraqi Army levels to delayed air-defense purchases. The region is now more exposed than at any time since 2014, and also more tied to Baghdad than at any time since 2003.

How Baghdad handles this situation will be important. The federal government now has greater leverage over Kurdish budgets, salaries, and air defense. If used to deepen federal integration, that leverage could strengthen the state’s sovereignty claims. If used coercively, it could instead revive the grievances that culminated in the confrontation over the Kurdish independence referendum in 2017.

Sovereignty Without a Backstop

Without the U.S. presence, which gave Iran-aligned factions a cause, the Kurds a patron, and Baghdad a counterweight to Tehran, power is being renegotiated from within Iraq and from without.

Although U.S. military forces have withdrawn, Washington’s leverage has not vanished. Despite the troop withdrawal, Washington keeps significant leverage over Baghdad because it controls Iraq’s oil revenues. Since the 2003 invasion, Iraq’s oil proceeds have been held in a Central Bank of Iraq account at the Federal Reserve Bank of New York. Oil makes up about 90 percent of Iraq’s state budget. When Baghdad asked U.S. troops to leave in 2020, Washington reportedly threatened to cut off its access to those funds, and Iraq backed down. Earlier this year, the U.S. halted dollar shipments to pressure Baghdad over Iran-aligned groups, including a plane carrying nearly $500 million in banknotes, which the Treasury blocked. Shipments resumed in June, but Washington signaled it could still impose sanctions over pro-Iran militias.

The withdrawal also does not translate into a vacuum that Iranian influence will automatically fill, particularly while Tehran remains under the pressure of war and sanctions itself. But it removes one of the principal constraints around which Iraq’s post-2003 political balance developed. Moreover, Iraq is acutely vulnerable to the external pressures stemming from the conflict raging beyond its borders.

That makes Baghdad’s claim to sovereign control especially difficult to realize. Iraq’s security forces have accumulated a decade of combat experience fighting ISIS, the government has limited coercive options against the strongest Iran-aligned armed groups. As Lahib Higel of the International Crisis Group has argued, pushing al-Zaidi into a direct confrontation with those militias risks a fight the government is unlikely to win.

Iraq also still lacks meaningful air-defense capabilities, with promised foreign systems yet to be delivered. The government remains without a defense minister, leaving it unclear who ultimately owns the disarmament file. Its room for maneuver is also constrained by a fiscal crisis: oil provides the bulk of the government’s budget, but disruption in the Strait of Hormuz cut oil exports from roughly 3.3 million barrels per day to about 600,000 in March, leaving Baghdad with limited resources to absorb fighters into state payrolls.

That explains the government’s preference for a sequenced, political strategy: postpone the disarmament deadline, secure a temporary truce, bargain with factions willing to integrate, and use the withdrawal to erode the legitimacy of those that refuse. While this is likely the only viable approach, it needs time, and every strike on Iraqi soil strengthens the very argument that Baghdad is trying to dismantle—that autonomous armed factions remain necessary because the state cannot defend the country.

Sovereignty as a Test, Not a Prize

The U.S. withdrawal settles one question that has shaped Iraqi politics for more than two decades: whether foreign troops will remain on Iraqi soil. It leaves unresolved the more consequential question of who, within Iraq, has the authority to use force. Baghdad claims a monopoly; the holdout factions seek to preserve their share; the Kurds want proof that federal sovereignty will protect them from any post-U.S. withdrawal security threats from Iran and its factions in Iraq. Iran and the United States, meanwhile, each expect to shape the outcome without bearing the costs of a permanent military presence.

Iraq has traditionally managed such conflicts through bargaining rather than imposed victories. But the withdrawal changes the terms of that bargain, by removing the most powerful justification for maintaining weapons outside of state control while placing a greater burden on Baghdad to demonstrate that it can provide the security those groups claim to supply.

That is the real test of the post-American period. If the state fails to control weapons by June 2027, it cannot blame foreign military occupation. If it succeeds, Iraqi sovereignty will, for the first time since 2003, be defined by Iraqis themselves.