The departure of the last U.S. forces from Iraq on September 30 marks more than the end of Operation Inherent Resolve. It marks the closing of one chapter in Iraq’s post-2003 security architecture and the beginning of a more uncertain phase in which Baghdad, the Kurdistan Region, Iran-aligned armed groups and the United States will have to operate without the physical presence of American forces on Iraqi soil.

The United States Central Command presented the withdrawal as an orderly and planned transition. In its official announcement, CENTCOM said U.S. forces and equipment had completed their departure from Erbil Air Base, formally ending the Operation Inherent Resolve mission in Iraq. CENTCOM stressed that the move is part of a transition toward a bilateral U.S.–Iraq defence relationship, while the broader coalition counter-ISIS mission continues from Jordan and in Syria.

That distinction is strategically important. The end of the coalition mission inside Iraq does not mean the disappearance of the U.S.–Iraq security relationship. Rather, Washington is moving from a large multinational military operation toward a bilateral security relationship in which Iraqi forces assume primary responsibility for national security.

The significance of that transition is underscored by ABC News Australia's account of the withdrawal, which describes the move as the conclusion of a 12-year campaign against ISIS and quotes Iraqi officials presenting it as a new phase defined by Iraqi sovereignty, stronger institutions and balanced international partnerships.

The central question, therefore, is not simply whether U.S. troops have left. They have. The more consequential question is what happens to the security system that developed around their presence.

From Coalition Security to Iraqi Responsibility

Washington and Baghdad have been preparing for this transition since the agreement to wind down the coalition mission. By September 2026, American forces had already departed most other locations in Iraq, leaving Erbil as the principal remaining operational hub.

For Baghdad, this provides an important political narrative. The Iraqi government can now argue that the country has moved from externally supported security toward nationally managed security. The withdrawal has accordingly been presented as a sovereignty milestone, with Iraq declaring a new era in which its own institutions assume primary responsibility for security.

But sovereignty and security capacity are not identical.

Iraq now inherits responsibility for intelligence, surveillance, air defence, border security, counterterrorism coordination and the management of armed actors operating within and outside the formal state security structure.

The Associated Press account of the U.S. withdrawal captures this tension particularly clearly. While Iraqi and U.S. officials presented the withdrawal as a transition toward Iraqi-led security, AP also reported continuing concerns over ISIS, Iran-backed militias and the unresolved question of militia disarmament.

The current transition is therefore fundamentally different from the immediate post-2011 environment. ISIS no longer controls large portions of Iraqi territory, and Iraqi security forces have acquired substantial combat experience. CENTCOM itself argues that ISIS no longer poses a systemic threat to Iraq and that Iraqi forces, including the Peshmerga, possess the capacity to manage threats independently.

But military capacity against ISIS does not automatically provide strategic security against missiles, drones, foreign-backed armed groups or regional military pressure.

That distinction is particularly important for Kurdistan.

The Kurdish Security Question

For the Kurdistan Region, the American withdrawal carries a significance that extends beyond the end of the anti-ISIS campaign.

The Peshmerga became one of Washington's most important Iraqi partners after the rise of ISIS in 2014. Coalition intelligence, training, equipment, air support and operational coordination contributed to the Kurdish forces' ability to defend the region and participate in the campaign against ISIS.

The end of the coalition mission therefore removes more than American personnel. It removes part of the wider security infrastructure that had developed around the U.S.–Peshmerga relationship.

This concern is reflected directly in ABC News Australia's report on the withdrawal, which reported Kurdish concerns about the removal of American air-defence systems. Kurdish officials said the Kurdistan Region had experienced more than 1,000 drone and ballistic-missile attacks during the recent U.S.–Iran conflict.

The concern is even more explicit in Al Jazeera's analysis of the new security environment for the Peshmerga. The report notes that the United States removed key air-defence systems when it withdrew and that Kurdish officials and analysts are questioning what the reduction of the American military presence means for Washington's long-standing security relationship with the Kurdistan Region.

This creates an important distinction between the ISIS question and the wider Kurdish security question.

The Peshmerga may possess sufficient capabilities to conduct counter-ISIS operations, as the U.S. military maintains. But counterterrorism capacity is not equivalent to protection against ballistic missiles, drones, advanced surveillance requirements or state-linked military pressure.

For Kurdistan, therefore, the issue is not simply whether the Peshmerga can fight ISIS without American soldiers beside them. It is whether the region possesses sufficient independent capabilities to operate in an increasingly sophisticated regional security environment.

Peshmerga Unification at a Critical Moment

The timing of the Peshmerga unification announced on September 21 is consequently significant.

Only days before the coalition's final withdrawal, the Kurdistan Regional Government announced that forces historically associated with the Kurdistan Democratic Party and Patriotic Union of Kurdistan were being brought under a unified structure.

Al Jazeera's detailed examination of the Peshmerga's new era reports that KRG President Nechirvan Barzani presented the move around the principle of one force, one ministry and one command, describing the Peshmerga as a national force that should stand above party disputes.

The political importance of this development extends beyond internal Kurdish administration.

For years, the existence of KDP- and PUK-linked security structures has complicated the development of a genuinely unified Kurdish defence institution. Separate geographical commands and political affiliations have also affected the relationship between Erbil, Sulaymaniyah and Baghdad.

The end of the coalition mission makes this problem more urgent.

As Al Jazeera reports, Kurdish officials insist that the Peshmerga is ready for the new period, while analysts interviewed by the publication identify the continuing separation between the two geographical commands as one of the principal tests of the unification process.

The practical test, therefore, will not be whether a unification ceremony has taken place. It will be whether operational command, intelligence, logistics, training, budgeting and deployment can actually function through a unified institution.

This is especially important because the Peshmerga will now have to demonstrate greater institutional independence at precisely the moment when external military support is becoming less visible.

Baghdad's Sovereignty Test

For Baghdad, the withdrawal creates an equally important institutional test.

The Iraqi government can now legitimately argue that the state has assumed primary responsibility for national security. Yet the state does not operate in an environment in which all armed power is concentrated under one uncontested chain of command.

The militia question remains unresolved.

AP reported before the withdrawal that powerful Iran-backed militias were refusing to disarm, despite the Iraqi government's efforts to move toward greater centralisation of armed force. The report noted that groups including Kataib Hezbollah and Harakat al-Nujaba had rejected disarmament or attached conditions that made an immediate settlement difficult.

The issue subsequently became part of the broader post-withdrawal security debate. AP's report following the withdrawal reported that the government had pushed the militia disarmament deadline to June 2027 after resistance from powerful factions.

This produces one of the central contradictions of the post-coalition environment.

Iraq is simultaneously declaring greater sovereignty while continuing to confront the existence of powerful armed organisations whose political and military influence extends beyond the conventional state security structure.

For Iran-aligned factions, the American withdrawal removes one of the principal arguments historically used to justify armed resistance against the U.S. presence.

But the disappearance of American troops does not automatically resolve the question of who ultimately controls armed force in Iraq.

As Al Jazeera's post-withdrawal analysis notes, the end of the American military presence could remove one justification used by armed groups to retain weapons, but the outcome will depend on whether Iraq replaces that confrontation with institutional law and political dialogue.

That is why Baghdad's sovereignty test begins after the foreign troops leave, not before.

Iran's Strategic Environment

Iran is an unavoidable part of this equation.

The withdrawal has taken place amid direct U.S.–Iran confrontation, making Iraq an especially sensitive arena for competing regional interests. The presence of Iran-aligned armed groups inside Iraq means that developments between Washington and Tehran can continue to affect Iraqi security even after American troops have left.

The reaction of Iran-aligned groups to the withdrawal is therefore significant.

AP reported that Iran-backed groups celebrated the American departure, presenting it as a restoration of Iraqi sovereignty while simultaneously maintaining political pressure on the Iraqi government.

This creates an ambiguous strategic environment.

For Baghdad, the withdrawal represents sovereignty.

For Washington, it represents a transition from a wartime coalition mission to a bilateral relationship.

For Iran-aligned groups, it represents the departure of their principal foreign military adversary from Iraqi territory.

For the Kurdistan Region, however, the same development is experienced partly through the question of what happens when a major external security presence becomes smaller.

All four interpretations can exist simultaneously.

That is what makes the post-withdrawal environment more complicated than a simple transfer of responsibility from Washington to Baghdad.

The ISIS Question Has Not Disappeared

The end of Operation Inherent Resolve should not be interpreted as the end of the ISIS problem.

The U.S. military's assessment is that ISIS no longer represents a systemic threat to Iraq. That reflects the transformation of the battlefield since 2014, when ISIS controlled large areas of Iraq and Syria.

But the continued existence of ISIS networks means that Iraqi security forces must maintain intelligence-led counterterrorism operations.

This is where the distinction between combat operations and the wider coalition support system becomes important.

The coalition's contribution was never limited to American soldiers physically fighting ISIS. Intelligence, surveillance, reconnaissance, targeting, logistics, training and operational coordination were also central components of the campaign.

The question facing Iraq is therefore whether its institutions can reproduce these capabilities independently and sustainably.

This concern is reflected in AP's reporting on the post-withdrawal security environment, which notes that the ISIS threat has diminished substantially while questions remain about Iraq's ability to manage the broader security environment without the American military presence.

The challenge is particularly significant in areas where Iraqi federal forces and the Peshmerga must coordinate against ISIS remnants.

The disappearance of a permanent coalition presence therefore increases the importance of direct Iraqi-Kurdish security coordination.

The New U.S.–Iraq Relationship

The most important misconception about the withdrawal would be to describe it simply as the disappearance of the American role in Iraq.

The official U.S. position is more complicated.

CENTCOM's official announcement explicitly describes the withdrawal as a transition toward a bilateral defence relationship. The counter-ISIS task force remains active in the region, headquartered in Jordan, while the United States says it will continue to maintain the capability to respond to ISIS threats.

The United States is therefore moving from a large-scale coalition military architecture toward a more conventional state-to-state relationship.

That changes the nature of American influence in Iraq without necessarily eliminating it.

Security cooperation can increasingly occur through defence agreements, intelligence sharing, training, military assistance and diplomatic engagement rather than through a large permanent American military footprint.

This distinction is particularly important for the Kurdistan Region.

The end of the coalition mission does not necessarily mean the end of Washington's relationship with the Peshmerga. But it does mean that the relationship must operate within a different institutional framework, increasingly through Baghdad and the bilateral U.S.–Iraq relationship.

For Erbil, this creates a strategic challenge: maintaining strong relations with Washington while simultaneously strengthening constitutional relations with Baghdad.

The Security Gap Left Behind

The most consequential issue after September 30 may therefore not be the number of American soldiers who have left.

It may be the capabilities that leave with them.

The U.S. military presence represented a network of intelligence, surveillance, air defence, logistics, command-and-control and rapid-response capabilities. Some of these functions can be transferred to Iraqi institutions. Others require significant technological, financial and institutional investment.

The Kurdish concern over air defence illustrates this gap particularly clearly.

ABC News Australia reported that Kurdish officials specifically objected to the departure of American air-defence systems, citing the region's experience of repeated drone and missile attacks.

Al Jazeera likewise reported that the removal of U.S. air-defence capabilities was a major concern in Erbil.

The significance is broader than Kurdistan.

A modern security architecture cannot rely solely on infantry and conventional counterterrorism forces. It requires early warning, intelligence fusion, air surveillance, electronic capabilities, missile defence and rapid response.

Iraq's ability to develop these capabilities will therefore become one of the most important measures of the post-coalition security transition.

A New Strategic Balance

Iraq is consequently entering a period in which sovereignty and vulnerability will exist simultaneously.

The absence of foreign troops gives Baghdad greater political ownership of the security environment. But greater ownership also means greater responsibility.

The Kurdistan Region faces the same reality at a different level.

The Peshmerga's unification creates an opportunity to strengthen institutional coherence precisely as external military support decreases. But the success of that process will depend on whether the new structure becomes genuinely national rather than simply placing existing party-based forces under a new administrative framework.

The withdrawal also changes the political calculations of Iraq's armed groups. Their traditional justification for maintaining a permanent anti-American posture becomes less relevant when American forces are no longer stationed in Iraq. The unresolved question is whether that produces greater integration into the state or a new competition over political influence.

Meanwhile, Iran remains an unavoidable regional actor, while Washington remains an important external partner even without permanent combat forces in Iraq.

The result is not a vacuum in which one actor simply replaces another.

It is a more fragmented and contested security environment in which Iraq itself must become the principal manager of competing relationships.

Conclusion

The end of Operation Inherent Resolve in Iraq is therefore best understood as a transition from externally supported security to nationally managed security.

Washington has declared that the coalition's mission has achieved its principal objective and that Iraqi forces are capable of assuming primary responsibility. Baghdad has embraced the withdrawal as a restoration of sovereignty. Iran-aligned groups have celebrated the departure of American forces. The Kurdistan Region, meanwhile, has entered the new era with both an institutional opportunity through Peshmerga unification and significant concern over the loss of American military capabilities.

The immediate future will test whether these different interpretations can coexist within a functioning Iraqi state.

For Baghdad, sovereignty must now be measured by its ability to control armed force, protect national airspace and secure its borders. For the Kurdistan Region, security will increasingly depend on the institutional effectiveness of a unified Peshmerga, deeper coordination with Baghdad and the durability of its relationship with Washington. For the United States, the challenge is to maintain strategic influence and counterterrorism cooperation without recreating the large military footprint that has now ended.

The most important change, therefore, is not simply that American troops have left Iraq.

It is that Iraq has inherited responsibility for a security system that previously depended heavily on an international coalition.

The first test of that system will not necessarily come from ISIS. It will come from whether the Iraqi state can convert sovereignty from a political declaration into operational capacity.

Iraq has entered the post-coalition era.

Now the question is whether its institutions can carry the weight of the security order that has been left behind.

Dr. Pshtiwan Faraj is Founder and Director of Kurdish Policy Analysis and a researcher specializing in Iraq, Kurdistan, Middle Eastern security, geopolitics and international relations.