Complex sentence: The Battle Group was established in July 2006 and was based at Tallil Airbase in Dhi Qar Governorate, consisting of units previously assigned to the third, and final, rotation of the Al Muthanna Task Group.
Split into simpler sentences: The Battle Group was established in July 2006 and was based at Tallil Airbase in Dhi Qar Governorate. Upon its formation Overwatch Battle Group (West) consisted of units which were previously assigned to the third, and final, rotation of the Al Muthanna Task Group.