A partial evacuation of British citizens was completed by 17 January, when the army riots in Southeast Africa prompted "Rhyl"'s diversion to Tanganyika so the troops she was carrying could assist in quelling the mutiny. In replacement, a company of the Gordon Highlanders was loaded aboard "Owen" so an intervention could still be made if necessary. The aircraft carriers "Centaur" and "Victorious" were also transferred to the region as part of Operation Parthenon. Although never enacted, Parthenon was intended as a precaution should Okello or the Umma party radicals attempt to seize power from the more moderate ASP. In addition to the two carriers, the plan involved three destroyers, "Owen", 13 helicopters, 21 transport and reconnaissance aircraft, the second battalion of the Scots Guards, 45 Commando of the Royal Marines and one company of the second battalion of the Parachute Regiment. The island of Unguja, and its airport, were to be seized by parachute and helicopter assault, followed up by the occupation of Pemba. Parthenon would have been the largest British airborne and amphibious operation since the Suez Crisis.