Australian interests in the Middle East in general and the Suez area in particular have traditionally been of two kinds: military and economic. Imperial and Australian defence planning in the first half of the twentieth century had been based on the assumption that there would be a string of imperial bases between London and Singapore or Darwin which would make effective Commonwealth defence plans in the Mediterranean, Indian Ocean and Pacific Ocean areas. Gibraltar, Malta, Suez, Aden, Colombo and Singapore had been the normal naval and/or air bases regarded as vital to the safeguarding of the Dominions east of Suez. Commonwealth security had been maintained through dominant British influence at key strategic points along what had frequently been described as the jugular vein of the Commonwealth. It was for this reason that Australian forces had served in the Middle East in two world wars. Political and economic stability in the sensitive Middle Eastern area was regarded as a matter of vital concern to the Commonwealth as a whole.