One of Mr Sadr's top men, Salah al-Obeidi, said that a criminal gun-running network that has operated in the region for years probably acquired the arms.
Marines from 40 Commando took on responsibility for Battle Group North in Helmand Province from last September until this April, where they operated from spartan forward operating bases in the Gereshk and Sangin valleys, often taking part in fierce gun battles with the Taliban, and playing a key role in the recapture of the town of Musa Qala.