OEF

OEF most commonly refers to Operation Enduring Freedom, the United States–led military operation in Afghanistan and related actions that followed the September 11, 2001 attacks. The campaign began in October 2001 with a coalition invasion intended to dismantle al-Qaeda’s bases in Afghanistan, remove the Taliban from power, and enable the establishment of a stable, Afghan-led government and security forces. The mission involved U.S. and allied military forces, Afghan government partners, and an expanding international effort that included counterterrorism, stabilization, and reconstruction activities.

In its Afghan phase, OEF sought to deny extremist networks a sanctuary and to support Afghan governance, security, and development. NATO’s International Security Assistance Force (ISAF) provided security, training, and capacity-building for Afghan forces for much of the period, while later efforts emphasized mentoring and advising through the Resolute Support Mission rather than large-scale combat operations. The campaign achieved early milestones, such as removing the Taliban from power in major urban centers, but the insurgency persisted and governance, civilian protection, and development challenges remained ongoing.

From 2014 onward, international forces increasingly shifted from combat operations to training and advisory roles, culminating in the withdrawal of most foreign troops and a transition of primary responsibility to Afghan forces and institutions. The 2021 U.S.-led withdrawal significantly altered the security landscape in Afghanistan. The Enduring Freedom designation has also been used for related, separate operations in other theaters, though those efforts are distinct from the Afghanistan campaign.

Note: OEF can refer to other, non Afghanistan-related uses in different contexts.