Iraq War: A suicide bomber kills 22 at the forward operating base next to the main U.S. military airfield at Mosul, Iraq, the single deadliest suicide attack on American soldiers in Iraq.

The Iraq War, also referred to as the Second Gulf War, was a prolonged conflict in Iraq from 2003 to 2011. It began with the invasion by a United States-led coalition, which resulted in the overthrow of the Ba'athist government of Saddam Hussein. The conflict persisted as an insurgency that arose against coalition forces and the newly established Iraqi government. US forces were officially withdrawn in 2011. In 2014, the US became re-engaged in Iraq, leading a new coalition under Combined Joint Task Force – Operation Inherent Resolve, as the conflict evolved into the ongoing Islamic State insurgency.

A suicide attack is a deliberate attack in which the perpetrators intentionally end their own lives as part of the attack. These attacks are a form of murder–suicide that is often associated with terrorism or war. When the attackers are labelled as terrorists, the attacks are sometimes referred to as an act of "suicide terrorism". While generally not inherently regulated under international law, suicide attacks in their execution often violate international laws of war, such as prohibitions against perfidy and targeting civilians.

The Forward Operating Base Marez bombing took place on December 21, 2004. Fourteen U.S. soldiers, four U.S. citizen Halliburton employees, and four Iraqi soldiers allied with the U.S. military were killed by a suicide bomber in a dining hall at the Forward Operating Base next to the main U.S. military airfield at Mosul.

A forward operating base (FOB) is any secured forward operational level military position, commonly a military base, that is used to support strategic goals and tactical objectives. A FOB may contain an airbase, hospital, machine shop, and other logistical facilities. The base may be used for an extended period of time. FOBs are traditionally supported by main operating bases that are required to provide backup support to them. An FOB also improves reaction time to local areas as opposed to having all troops on the main operating base.