Michael Brill
For President Donald Trump, Operation Inherent Resolve, the military campaign against the Islamic State in Iraq and al-Sham (ISIS), was a rhetorical foil against the calamitous August 2021 withdrawal from Afghanistan under the administration of President Joe Biden. Appearing on Joe Rogan’s podcast shortly before the election, Trump repeatedly drew this contrast and highlighted the lack of accountability for Afghanistan, at one point stating, “The real generals, not the ones you see on television, the ones that beat ISIS with me. We defeated ISIS in record time. It was supposed to take years, and we did it in a matter of weeks.”
Upon returning to the White House in January 2025, Trump once assumed responsibility for operations against ISIS, which ticked steadily upward in 2024, with US airstrikes in Syria and raids in Iraq. Nearly 1,000 US troops are deployed in Syria and 2,500 in Iraq for the purpose of executing this mission. In March, US and Iraqi forces conducted a joint operation that killed two ISIS leaders in Western Iraq, the most significant campaign event in Trump’s second term to date. Despite prioritizing support for Israel’s resumed war against Hamas, the return to “maximum pressure” against Iran, and expanded operations against the Houthis in Yemen, inherited deadlines from the Biden administration will require political attention and diplomatic engagement in Iraq and Syria beyond following existing policy and continuing strikes against ISIS alone.
Waning Resolve for Operations Against ISIS?
Facing pressure from Iranian-backed factions, Iraq’s Prime Minister Mohammed Shia al-Sudani committed to the departure of international forces from Iraq by September 2025, with the continuation of logistical support of US operations in Syria from northern Iraq until at least September 2026. If not addressed proactively by the Trump administration in a way that ensures the continuation of operations, these deadlines could become time-bombs like that of the Doha Accords for Afghanistan, which the first Trump administration bequeathed the Biden administration. The surprise rebel offensive and collapse of the Assad regime in Syria, where Turkey is the largest external power broker, could complicate and threaten the US mission directed toward ISIS. It also seems plausible that the upending of Syria’s relatively stalemated conflict, where Russia’s distraction with Ukraine, along with Hezbollah and Iran’s losses against Israel have all been factors, could precipitate renewed appeals by Turkish President Recep Tayyip Erdoğan to Trump, calling for the removal of US troops from Syria, to which he proved agreeable during his first term.
Considering these developments, reexamining the history of the war against ISIS is timely and potentially contains insights on its next stages under the second Trump administration. It is also worth comparing political rhetoric about the fight against ISIS with its military reality, as the former still obscures accurate perceptions of the latter. The war against ISIS required the deployment of assets from all branches of the US military, complex planning and close coordination with allied militaries and local security partners alike, and the execution of operations on difficult terrain over vast distances. The operation’s relative stability across the previous three administrations has been a key factor in its comparative success.
The War Against ISIS: Rhetoric and Reality
As a candidate for the Republican presidential nomination in November 2015, Trump’s campaign released a radio ad in which he accused President Obama and other politicians of “losing the war on terrorism.” He also promised to “quickly and decisively bomb the hell out of” ISIS. Upon winning the presidential election and taking office in January 2017, President Trump followed through on a campaign pledge to convene his generals and order them submit a new plan for defeating ISIS. However, this did not substantively alter ongoing operations. Following the fall of Baghuz and killing of ISIS caliph Abu Bakr al-Baghdadi in 2019, for the remainder of his first term, Trump reiterated the theme, “When I took office, we had almost nothing. It was at though they were just forming again, and now it’s 100 percent.”
Political rhetoric notwithstanding, Operation Inherent Resolve was characterized more by continuity than change across the Obama and Trump administrations. This process was first and authoritatively documented by Michael R. Gordon’s 2022 book Degrade and Destroy: The Inside Story of the War Against the Islamic State, from Barack Obama to Donald Trump. Counter-ISIS operations, along with US deployments in Iraq and Syria, continued under the Biden administration, which notably rushed US forces to help quell the attempted ISIS jailbreak in Hasaka, followed shortly thereafter by a raid that killed the ISIS caliph Abu Ibrahim al-Hashimi al-Qurayshi, in early 2022. The success of the US military and its allies in maintaining pressure against ISIS is even more remarkable given the growing harassment by Iran and Iranian-backed militias under both the Trump and Biden administrations. Following the collapse of the Assad regime in December 2024, President Biden increased strikes against ISIS in Syria.
America’s Long War Against ISIS
For as much as President Obama had staked politically in withdrawing all US troops from Iraq by the end of 2011 and attempting to avoid reengagement with the country’s political turmoil thereafter, he reluctantly deployed US forces back to Iraq after the fall of Mosul to ISIS in June 2014. After some early stumbles in the months after US forces returned to Iraq, during which ISIS continued to expand its territory into 2015, Obama’s administration devoted considerable effort to building the international coalition and developing plans for rebuilding and retraining the Iraqi Security Forces for the purpose of halting and then rolling back the ISIS caliphate.
Adapting a concept that emerged in the Special Forces community decades ago based on partnering a limited number of US troops with a larger local force, “by, with, and through” became central to the war against ISIS. Operations on the ground were carried out by local allies, with support from US troops and their partners, and through a legal framework. Neither an over the horizon drone campaign nor an application of the doctrine of overwhelming force, the US fought ISIS through proxies on the ground, supported not just by small teams of US advisers, but also the concentrated use of intelligence, artillery, and air power. The strategy also squared with the growing bipartisan aversion in Washington to so-called “forever wars,” along with the priorities of US politicians and voters, even if many were contradictory.
"By, with, and through” was employed as the means to defeat ISIS as quickly as possible with local allies doing the bulk of fighting and dying on the ground, prevent ISIS-directed or -inspired terrorist attacks against the US homeland, and keep the number of US troops deployed and casualties to a minimum while also relying on the precision targeting of ranged fire support that would in theory spare civilian lives and property to the greatest extent possible. That the latter expectations fell short against the reality of war, especially with an enemy that systematically entrenched itself in civilian environments and employed human shields, has resulted in renewed attention to civilian casualties. However, the alternative of deploying more US troops to do the fighting while relying less on ranged firepower, was as politically unviable to the Obama, first Trump, and Biden administrations then as it is for the second Trump administration today.
Rules of Engagement: Taking the Gloves Off?
Trump’s campaign rhetoric and claims as president contributed to the perception that he loosened the Rules of Engagement for taking the fight more aggressively to the enemy. However, Tactical Directive No. 1, the most important step in this direction, was issued by coalition commander Lieutenant General Stephen Townsend in December 2016. Although it took time for the order to be implemented and the deployment of US advisers directly to the battlefield’s frontlines, the decision was made during the final weeks of the Obama administration. Additionally, the plan and timetable for the military operations with Iraqi and Syrian partners to retake Mosul and Raqqa from ISIS, were developed and put in motion by US military officers with the help of Pentagon civilians primarily under the purview of the late Secretary of Defense Ash Carter, Obama’s final secretary of defense.
With the 2016 US Presidential elections looming, President Obama exerted no political pressure to alter or expedite the Pentagon’s planning or timetable for achieving the military defeat of the ISIS caliphate. Upon taking office, President Trump made no significant changes to the military’s strategy or Rules of Engagement that expedited the campaign. While the Obama administration had begun to scale back its political micro-management of the war in 2016, arguably Trump’s most impactful decision was to remove the level of White House oversight that had the effect of allowing the Obama-era strategy to be executed more efficiently.
Commanders in theater were empowered to devise and execute operations based on developments on the battlefield instead of facing long delays caused by navigating multiple levels of bureaucratic red tape. Although Trump’s hands-off approach entailed risks of its own, it also produced immediate results. In support of the Kurdish Syrian Democratic Forces (SDF) in the operation to retake Tabqa, the first air assault of the campaign, which was supported by Marine howitzers, Army attack helicopters, HIMARS surface-to-surface rockets, and US airpower, was both rapidly planned and approved. “I kept the SECDEF informed but did not have the CONOP approved in Washington. We took a lot of risk,” recalled CENTCOM Commander General Joseph Votel.
Another area of continuity between the Obama and Trump administrations was the decision to arm the Kurdish militia fighters of the SDF. Obama administration and military officials concluded that the SDF was the only ground force capable of taking back Raqqa from ISIS. However, the decision to provide the force with heavier arms and ammunition, even those needed for the Raqqa battle, was anathema to Turkish President Erdoğan, who viewed the SDF as engaged in a Kurdish state-building project on Turkey’s border. On January 17, 2017, during Obama’s last week in office, the president convened a meeting of the National Security Council to finally address the deferred question of arming the SDF.
Obama clearly favored arming the SDF, but did not want to tie the hands of the incoming administration. Three days later, on Inauguration Day, Obama gave his recommendation on arming the SDF to Trump directly during their limousine ride to the Capitol. Later, as Trump sat in the inaugural reviewing stand in front of the White House, he turned to James Mattis, his choice to serve as secretary of defense, and told him the Kurds were great fighters. While Mattis never understood why Trump had chosen that moment to raise the issue, the Trump administration shortly thereafter followed Obama’s recommendation to arm the SDF.
Although Trump’s hands-off approach helped to better implement the strategy devised and initiated during the final year of the Obama administration, the potential for the president to become disengaged, paired with his penchant for losing patience, became liabilities as the coalition pursued ISIS deeper into the Middle Euphrates River Valley in Syria. As far as the president was concerned, US forces should help the SDF take Raqqa and then “get the hell out.” By emphasizing the value of Syria’s oil, Trump’s advisers partially succeeded in maintaining his attention on the campaign. However, Trump’s decisions to curtail stabilization funding and announce the sudden withdrawal of US forces from Syria, for the first time, precipitated the departure of key advisers and complicated efforts to establish and maintain security after the final demise of the ISIS caliphate.
The War on Terror’s Silver Linings Playbook?
Operation Inherent Resolve marked its tenth anniversary in August 2024. In contrast to the other post-9/11 military campaigns, Operation Inherent Resolve has been an unambiguous success in achieving its primary objectives of destroying the ISIS caliphate and preventing its resurgence to date. And despite the political rhetoric to the contrary, continuity has been the defining feature of the campaign, especially during the transition between the Obama and Trump administrations, then again under the Biden administration.
Unlike many other US military campaigns, the generals who commanded the Operation Inherent Resolve coalition never became household names or enjoyed extensive media coverage, Trump’s bragging about them notwithstanding. Generals Sean MacFarland, Stephen Townsend, Joseph Votel, Paul Funk, and Michael Nagata have all retired from active duty. Ironically, Chris Donahue, whose service with Delta Force was crucial in the early months of the war against ISIS, helping halt its advance while also laying the groundwork for pursuing the group into Syria, was singled out for accountability over the Afghanistan withdrawal. Senator Markwayne Mullin put a hold on Donahue’s promotion to four-star general and commander of US Army forces in Europe and Africa. The behind-the-scenes advocacy leading Mullin to quietly withdrawal the hold without comment may very well have enlightened the senator to the fact that Donahue is one of the generals from the war against ISIS President Trump often touts.
The battlefield successes of Special Operators, Marine Raiders and artillery, Army artillery and attack helicopters, Air Force pilots, and Navy aviators across vast distances and difficult terrain remain little known and under-appreciated even in the Defense establishment, overshadowed by discussion about the return to great power competition. That US forces involved in Operation Inherent Resolve, their local allies, and international coalition partners achieved the primary objectives despite the often-contradictory stipulations of American politicians and demands of voters alike, made their efforts more impressive still. Today, the second Trump administration, against the backdrop of policy priorities elsewhere in the Middle East and world, must navigate Iraq and Syria’s evolving politics and prevent their exploitation by ISIS, ensuring the hard-earned successes of Operation Inherent Resolve are not squandered.
Michael Brill is a Ph.D. Candidate in the Department of Near Eastern Studies at Princeton University. In 2024-2025, he was a Global Fellow in the History and Public Policy Program at the Woodrow Wilson International Center for Scholars, and a Non-Resident Fellow at the Institute for Future Conflict. He assisted Michael R. Gordon with the research and writing of his 2022 book Degrade and Destroy: The Inside Story of the War Against the Islamic State, from Barack Obama to Donald Trump, published by Farrar, Straus and Giroux. The views expressed in this piece are those of the author and do not reflect the official policy or position of the US Air Force, the US Department of Defense, or the US government.