The last U.S. troops have left Iraq, closing one chapter of an American military presence that began with the 2003 invasion and returned in a different form in 2014 to fight the Islamic State group. For Iran and its allies, the departure has been presented as a strategic victory. But removing American troops does not automatically translate into greater Iranian control.

The more important question begins now: what happens to Iran’s influence in Iraq when opposition to a U.S. military presence is no longer enough to justify armed power outside normal state institutions?

That question matters because Iran’s role in Iraq has never depended on a single tool. Tehran has relationships with political parties, armed factions, religious institutions and economic networks. Some Iran-aligned militias have also developed their own domestic interests that cannot be reduced simply to instructions from Tehran.

PeikNet’s earlier examination of Iran-backed militias and Iraq’s disarmament problem identified September 30 as an important test. With the American departure now completed, that test has moved from prediction to reality.

The U.S. Withdrawal From Iraq Removes a Powerful Militia Argument

The U.S. military said on September 30 that its withdrawal from Iraq had been completed. American troops had already left most facilities before the final departure from the Erbil area in Iraq’s semi-autonomous Kurdish region. The withdrawal ends the current U.S. military deployment inside Iraq, although Washington and Baghdad are expected to maintain a broader bilateral relationship that includes forms of security cooperation.

That changes the political argument available to armed factions that have long described the American military presence as a reason to remain mobilized.

Several Iran-aligned groups resisted Iraqi government pressure to surrender weapons ahead of the withdrawal. The dispute exposed a deeper sovereignty problem for Baghdad: removing foreign troops does not by itself establish that the Iraqi government has sole authority over armed force.

Reuters reported earlier in September that Prime Minister Ali al-Zaidi was struggling to persuade powerful Iran-aligned Shiite militias to disarm. Some groups argued that the departure of U.S. troops was a prerequisite for any discussion of their weapons.

That condition has now been met.

If those groups continue refusing disarmament, the debate changes. Their weapons can no longer be explained primarily as a response to American forces stationed inside Iraq. Baghdad can increasingly frame the issue around whether armed organizations answer to the elected state or retain separate military authority.

Iran Does Not Need U.S. Troops in Iraq to Remain Influential

It would be too simple, however, to conclude that Iran’s position suddenly weakens because militias lose one justification for retaining their weapons.

Tehran’s influence inside Iraq is much broader than the presence of armed groups.

Iran has spent years building relationships across Iraqi politics, commerce, religious institutions and security networks. Some Shiite factions with historic connections to Tehran participate openly in Iraq’s political system. Iran and Iraq also share extensive religious, commercial and social ties that existed long before the latest American military mission.

This means the real post-withdrawal question is not whether Iranian influence disappears. It is whether that influence becomes more political and institutional and less dependent on an openly armed resistance narrative.

That could produce a less visible form of influence.

A political party able to shape legislation, government appointments or economic policy does not need to fire rockets to matter. A business network capable of moving goods, money or energy across the Iran-Iraq border can create leverage without attracting the attention generated by militia operations.

Iran may therefore gain in one area while losing ground in another.

The departure of American troops removes one of Tehran’s most useful political symbols. At the same time, it removes a competing military presence that constrained Iran-aligned armed groups.

Which effect proves more important will depend largely on what Baghdad does next.

Baghdad Now Faces the Harder Sovereignty Test

For Iraq’s government, getting foreign troops to leave was the clearer part of the sovereignty debate.

Controlling every armed organization inside Iraq could be much harder.

Some militias are deeply embedded in Iraq’s security and political landscape. Elements of the Popular Mobilization Forces are formally connected to the Iraqi state, while individual factions maintain different levels of political autonomy and relationships with Iran.

That creates a difficult distinction between integrating armed groups into state structures and simply placing a government label over forces that continue making important decisions independently.

The Associated Press reported before the withdrawal that several militias were already signaling that the American departure would not necessarily lead them to surrender their weapons.

That may become the most useful measure of the withdrawal’s effect.

If Baghdad can establish clearer command over armed factions, the American exit could strengthen Iraqi state authority without automatically transferring power to Tehran.

If armed organizations continue operating independently, the removal of U.S. forces could instead expose how much military authority remains outside Baghdad’s effective control.

Iraqi Kurdistan Has More at Stake Than Most

The security consequences are particularly important in the Kurdistan Region.

The final American departure came from Erbil, where U.S. forces had maintained a presence connected to counter-Islamic State operations and regional security. Kurdish officials have historically maintained close security relationships with Washington while also navigating difficult relationships with Baghdad, Tehran and neighboring Turkey.

The end of the American military presence changes that balance.

Islamic State no longer controls the vast territory it captured a decade ago, but both Reuters and the Associated Press reported continuing concerns about cells and militant activity after the withdrawal.

For Kurdish authorities, therefore, the issue is not only Iranian influence.

It is whether Iraqi forces, Kurdish Peshmerga and intelligence services can contain security threats without the same direct American military presence.

A serious resurgence by Islamic State could also produce an unexpected political consequence: militias could use renewed insecurity to argue that their weapons remain necessary.

That would complicate Baghdad’s disarmament effort even further.

American Military Power Is Gone, but American Leverage Is Not

The withdrawal also highlights a distinction that is easy to miss.

Leaving Iraq militarily does not mean the United States has stopped influencing Iraq.

Washington retains important diplomatic, financial and security relationships with Baghdad. One of the most consequential involves Iraq’s oil income.

Reuters reported on September 30 that Iraqi oil revenues continue to flow through arrangements involving the Federal Reserve Bank of New York. Oil provides the overwhelming majority of Iraqi government revenue, giving the financial relationship considerable importance even after American troops have departed. Reuters’ examination of Iraq’s oil-revenue system

That means Iraq is not simply moving from an American sphere into an Iranian one.

Baghdad remains economically and diplomatically connected to Washington while maintaining geographic, religious, economic and political ties with Iran.

Prime Minister al-Zaidi’s government has already demonstrated how difficult that balancing act can become. Washington has pressured Iraq to prevent sanctions evasion and constrain Iran-aligned armed groups, while Baghdad must manage domestic Shiite political constituencies and relations with neighboring Iran.

The U.S. withdrawal from Iraq changes one major part of that equation without eliminating the others.

Iran’s Influence May Become Harder to Measure

Iran and its allies can credibly point to the American military departure as an outcome they sought for years.

Whether that represents a lasting expansion of Iranian power is a different question.

Tehran could emerge with more freedom to work through allied political and security networks. But Iran-aligned militias also lose an important argument for maintaining independent military structures. Baghdad now has greater reason to demand that security authority move toward the state.

Meanwhile, Washington still possesses diplomatic and economic tools that do not require soldiers on Iraqi bases.

The most revealing developments over the coming months will therefore be practical rather than rhetorical: whether militias give up weapons or consolidate them, whether Baghdad can enforce state authority, whether Islamic State activity increases, how Kurdish security changes and whether Tehran increasingly relies on politics and economics instead of armed pressure.

PeikNet’s broader coverage of the Iranian response to U.S. pressure has shown how Tehran increasingly combines military leverage, economic pressure and diplomacy rather than relying on one instrument alone. Iraq may now become another test of that strategy.

The departure of American troops unquestionably changes Iraq’s strategic environment.

What it does not establish is that Washington has disappeared from Iraq or that Tehran has inherited the country.

The more important contest now takes place inside Iraqi institutions: who controls weapons, money, political decisions and security when the foreign army that dominated the debate is no longer there?

The answer to that question will reveal far more about Iran’s real regional influence than the withdrawal ceremony itself.