 During February and March 2003, tactical control (TACON) of the MEU was assigned to the United Kingdom's 3 Commando Brigade Royal Marines for Operation Iraqi Freedom.On 21 March 2003, Marines from the 15th MEU crossed the border into Southern Iraq and secured the ports of Umm Qasr and Az Zubayr in order to destroy Iraqi resistance and enable follow-on humanitarian assistance to begin.In late-March 2003, the MEU again became part of the I Marine Expeditionary Force and moved to An Nasiriyah, Iraq to relieve the Marines of Task Force Tarawa.