The British then shifted their focus north up the Persian Gulf, invading Southern Mesopotamia by advancing up the Shatt Al Arab waterway to Mohammerah (future Khorramshahr) at its junction with the Karun River, short of Basra.
The members of these groups were active in the nowadays region of "Khorramshahr" (Al-Mohammerah) of "Khorramshahr County" (Muhammarah) of the Khuzestan Province, Iran.