Cyprus has been a problem for Turkey since 1954 and the entangled conflict attracted the attention of the United States as well. While the situation of the island required mediation and diplomacy, it not only concerned the two communities of Cyprus but also the two allies; the United States and Turkey to confront with the major crises often. One of them was the 1964 Letter Crisis and the other one was the Conflict of 1967 which brought Turkey and Greece to the threshold of war. It was mediated by American diplomacy and described as a success by George Ball. Deadlocks and crises hurt the relations between the two states and the diplomacy that the United States called successful, in actuality meant disappointments and therefore were unable to address all their priorities for Turkey. This thesis argues that a catastrophic success was the result of bilateral relations and for this purpose, the thesis; surveys the effects of Turkish and American diplomats by combining their memoirs and archives.