US commanders believe that Mr al-Douri has spent much of his time on the run in neighbouring Syria, where President Bashar al-Assad's regime offered logistical support for the anti-American insurgency. However, with Syria now in the grip of civil war, it is thought he may now be using safe-houses around the northern city of Mosul, where US troops first reported attacks by his militia group back in 2009. Last month, Iraqi troops hunting for Mr al-Douri searched his old villa near Tikrit.