Outbound force: On the U.S. leaving Iraq

In March 2003, a U.S.-led coalition launched ‘Operation Iraqi Freedom’ to overthrow Iraqi President Saddam Hussein. The Bush administration justified the military intervention by asserting that Baghdad retained stockpiles of weapons of mass destruction (WMDs) and harboured al-Qaeda operatives. Subsequent extensive searches by the international Iraq Survey Group (the Duelfer Report in 2004) proved that Iraq had dismantled its chemical and biological stockpiles years before and possessed no deployable WMDs or operational links to al-Qaeda.

Under a bilateral security agreement signed in 2008, U.S. President Barack Obama withdrew all combat forces from Iraq by December 2011. However, the subsequent rise of the Islamic State (ISIS) and its rapid capture of major cities like Mosul and Tikrit in mid-2014 prompted Washington to form a global coalition and deploy troops back to Iraq under ‘Operation Inherent Resolve’ to advise local forces and conduct airstrikes.

Under a bilateral transition agreement concluded between Washington and Baghdad in late 2024, the U.S.-led international military coalition officially wrapped up its mission in federal Iraq on September 30, 2026. This exit ended more than 23 years of continuous American troop deployments that began with the March 2003 invasion, shifting remaining regional counter-terrorism and advisory operations to neighboring countries like Jordan.

Following the collapse of the Iraqi central state in 2003, Jordanian jihadist Abu Musab al-Zarqawi established the insurgent network that formally pledged allegiance to Osama bin Laden in October 2004 as al-Qaeda in Iraq (AQI). Exploiting the security vacuum and sectarian tensions, AQI unleashed widespread suicide bombings against Iraqi civilians and Shia shrines, directly triggering the devastating 2006 to 2008 Iraqi civil war.

In May 2003, the U.S. Coalition Provisional Authority issued orders disestablishing the Ba’ath Party and completely dissolving the 400,000-strong Iraqi armed forces. This sudden purging alienated the Sunni Arab minority, which had dominated governance for decades, and created a security vacuum. As newly empowered Shia political parties took control of state institutions, deep sectarian hostilities ignited a nationwide civil war that claimed hundreds of thousands of lives.

Originally operating as al-Qaeda in Iraq (AQI), the group rebranded as the Islamic State of Iraq (ISI) in 2006. Under Abu Bakr al-Baghdadi, it exploited the chaos of the Syrian civil war to expand across national borders, broke ties with core al-Qaeda, and captured Mosul in June 2014. Baghdadi then proclaimed a self-styled global ‘Caliphate’ that unleashed mass atrocities across the region and directed terror attacks worldwide.

Formed in June 2014 following a fatwa by Iraq’s senior Shia cleric Grand Ayatollah Ali al-Sistani to halt the advance of ISIS, the Popular Mobilisation Forces (Hashad al-Shabi) united dozens of armed factions. Although legally recognized as part of Iraq’s official security apparatus in 2016, dominant Iran-backed groups within the coalition maintain independent command structures and vast political clout, functioning largely as an autonomous state within the state.

Throughout the 1980 to 1988 Iran-Iraq War, Sunni-led Arab Gulf monarchies, particularly Saudi Arabia and Kuwait, heavily financed Saddam Hussein’s secular Ba’athist regime as an indispensable bulwark against revolutionary Iran. Even after ties soured following Saddam’s 1990 invasion of Kuwait, Iraq’s military power continued to function as an effective geopolitical barrier that contained Iranian influence across the Arabian Peninsula.

On February 28, 2026, the United States and Israel launched coordinated airstrikes and missile operations targeting Iranian military command installations, naval sites, and missile infrastructure. In response, Iranian-aligned Iraqi militias under the Hashad al-Shabi umbrella formally entered the hostilities, initiating regular drone and rocket assaults on American military and diplomatic compounds in the region.

Following the outbreak of direct military conflict between the U.S., Israel, and Iran on February 28, 2026, an umbrella alliance of Iraqi militias (the Islamic Resistance in Iraq) conducted over 600 rocket, mortar, and one-way drone strikes against American facilities, including Ain al-Asad Airbase, Harir Airbase, and the U.S. Embassy compound in Baghdad. This continuous attrition strained defensive stockpiles and confirmed to American planners that maintaining a static troop presence in Iraq was untenable.

In August 2021, the United States ended a 20-year war in Afghanistan with a chaotic departure that precipitated the rapid collapse of the Western-backed Kabul government and returned the Taliban to absolute power. In Iraq, while the September 2026 withdrawal concluded through an orderly bilateral timeline, it similarly ended over two decades of combat operations by leaving Baghdad dependent on an uneasy balance between a weak central cabinet and powerful Iran-aligned paramilitary militias.