In 1952 Turkey was invited to become a member of the North Atlantic Treaty Organisation. This study examines the context of the Turkish demand for an American security guarantee and of American and British security interests in the Eastern Mediterranean in the late 1940s in the light of Cold War developments. The postwar weakness of Great Britain, who had until then guarantied the status quo in the area induced Ankara to tum to the United States as a guarantor of Turkish political independence and territorial integrity against a powerful Soviet Union. The Turks asked for a formal alliance with the Americans, but this proved to be a difficult task. In the eyes of American military and State Department officials Turkey was a barrier against Soviet penetration in the Middle East. Hence, it was thought necessary to strengthen her resistance to the Soviets through the provision of American military aid. However,, Washington was reluctant to stretch the United States' resources by extending its commitments to this area which was still thought to be a British military responsibility. Britain for her part responded to Turkish demands in accordance with her general interests in the Middle East. London regarded Turkey as a part of Middle East defence: hence, it favoured an American commitment to Turkey, but mainly as a means of getting the Americans involved in the area as a whole. The evolution of American military thinking regarding Europe and the Middle East in 1951, made Washington to revise its policies towards Ankara. The realisation of Turkey's importance for the organisation of defence both in Western Europe and the Middle East along with the fear that Turkey might turn neutral in the event of a conflict with the Soviet Union induced the Americans to meet Turkish demands in what appeared to be the easiest way, that is, inviting Turkey to join the Atlantic Alliance. The study concludes that in the late 1940s Ankara followed a pragmatic foreign policy. Turkish leaders had a clear perception of their country's interests and were particularly alert at exploiting the circumstances which would promote them. In contrast, the foreign policy of the United States towards the Eastern Mediterranean was still developing and lacked the determination of a great power. Britain, on the other hand, continued to plan like a great power although it was obvious that she was not in a position to do so any more.