Colonel Arthur Reginald Chater , used his camel corps to skirmish with and screen against the advancing Italians as the other British and Commonwealth forces pulled back towards Tug Argan . Brigadier Chater used his Camel Corps supplemented by small patrols of the Illalos ( a small force of tribal levies normally employed on police duties ) to skirmish with and screen against the advancing Italians as the other British and Commonwealth forces pulled back towards Tug Argan .