At first, the division's role was internal security, while its mounted units underwent mechanisation. The signal unit detached Troops that formed new signal units for service at Tobruk and on Crete. Then, after a German-backed coup d'état in Iraq in April 1941, the Royal Air Force (RAF) training base at Habbaniya came under siege by Iraqi Nationalist forces. A relief column, known as 'Habforce', was organised from the troops available in Palestine. On 8 May Brigadier 'Joe' Kingstone of 4th Cavalry Brigade (the only one yet motorised) was sent on ahead with his brigade HQ and signals leading a Flying column named 'Kingcol' to effect a relief of the airbase as soon as possible.