US Concludes 12-Year Iraq Mission Against ISIS Amid Rising Iranian Influence and New Regional Challenges

The US military is officially ending its anti-ISIS operations in Iraq on Wednesday, concluding a 12-year mission dedicated to defeating the Islamist extremists. Operation Inherent Resolve has been considered a success by many measures, having reduced ISIS to a shadow of its former self and long dismantling its self-proclaimed "caliphate" in Syria and Iraq. However, the completion of this latest chapter in America's military involvement in Iraq—dating back to the 1991 Gulf War and the 2003 US-led invasion—offers no guarantee of a simpler security landscape for Baghdad moving forward.

Although ISIS is now diminished to a low-level insurgency, the US withdrawal introduces fresh challenges for both Baghdad and Washington, particularly concerning Iran. On one hand, removing US forces eliminates a primary target for Iran-backed militias, potentially halting a cycle of tit-for-tat violence with the US and enhancing Iraq's short-term stability. Conversely, the departure of American troops removes a critical check on Iranian influence. Tehran has spent years cultivating ties with Iraqi political factions, security forces, and the Popular Mobilisation Forces, and Iranian attention is expected to increase now that the US has departed.

“The Iranians are maintaining interest in Iraq, and the US is losing interest,” said Michael Knights, an adjunct fellow at the Washington Institute and head of research at Horizon Engage, a New York-based strategic advisory. “Whenever that happens, it's not a good outcome, typically,” he added. Jason Campbell, a senior fellow at the Middle East Institute, noted that the withdrawal could offer at least one potential benefit: “By the US leaving, if there's one sort of silver lining, it's depriving the justification many of these [Iran-backed] groups have used for maintaining their arms in the first place.” However, Mr Campbell also warned of a short-term public relations win for Iran and its proxies in Iraq alongside emerging vulnerabilities across parts of the country.

Mr Campbell cautioned against assuming that the withdrawal of US troops automatically signals the end of American influence in Iraq. “I don't know that the presence of a few hundred US forces had all that much impact as much as their overarching desire by both Erbil and Baghdad to stay on Washington's good side,” he remarked. Without US bases near Erbil, the Kurds face heightened vulnerability, particularly due to the loss of air defenses that previously protected US forces in the region. Iraq has historically maintained delicate political and military ties with both the US and Iran, which have occasionally utilized Iraqi territory as a proxy battlefield. Prime Minister Ali Al Zaidi initially set a deadline for Iran-backed militias to disarm by September 30, though that timeline has since been extended to the end of June 2027.

Mr Knights noted that while Washington views Mr Al Zaidi as inexperienced, the US is likely to adopt a laissez-faire stance regarding the disarmament of Iran-backed militias, provided they refrain from targeting US interests. “The US, I think, is saying, as long as we don't have rocket and drone attacks coming out of Iraq or against our embassies in Iraq, we can cope with the existence of the militias,” he observed, suggesting the Trump administration has maintained a pragmatic perspective.

Operation Inherent Resolve began in August 2014 when the US initiated airstrikes against ISIS targets in Iraq as militants advanced across Syria and northern Iraq. Numerous nations contributed to the campaign, which marked America's return to Iraq following the 2011 troop withdrawal under then-president Barack Obama. Allied forces subsequently supported Iraqi, Kurdish, and Syrian partner forces. According to Pentagon figures, 123 US troops were killed and 499 wounded during the mission, while coalition estimates indicate over 80,000 ISIS members were killed. Nevertheless, Kurdish commander Sirwan Barzani warned that a lack of US intelligence, logistical support, and drones could enable ISIS to regroup, noting that sleeper cell activity has already been observed following the coalition's withdrawal announcement.