When President Jimmy Carter entered the White House, he desired a decision-making structure that would be collegial and provide him with a diverse range of policy options from his principal advisors, Secretary of State Cyrus Vance and National Security Advisor Zbigniew Brzezinski. However, their differing outlooks coupled with a desire to control and manage U.S. foreign policy led to a furious and bitter battle to influence the administration's agenda. This thesis analyses the relationship between Vance and Brzezinski and their struggles for the ear of the president. It was a conflict exacerbated by the institutional rivalry between the National Security Council and the State Department as they battled with one another to affect policy. As issues arose, the president's advisors, supported by their constituencies, jostled to orchestrate the administration's strategies and approach. Subsequently, tensions increased as the conflict between Vance, Brzezinski and their departments developed into unbridled bureaucratic warfare within the Carter administration. This study utilises the bureaucratic politics paradigm to illustrate how the influence of advisors and organisations can impact on presidential decision-making. While President Carter wanted to be the main decision maker in his administration, his insistence on a system that provided him with a range of advice precipitated the struggles between Vance and Brzezinski. As their disputes intensified, Carter was unable to effectively manage the views and advice of his advisors and formulate a clear strategy. As this thesis demonstrates, the bureaucratic politics model provides an effective framework to analyse the development and implementation of U.S. foreign policy. While historians have neglected or played down the significance of their clashes, this thesis argues that the rivalry between Vance, Brzezinski, and their respective departments had a clear and visible effect on U.S. foreign policy. The bureaucratic wars raged throughout Carter's time in office, contributing to a tapestry of inconsistencies that resulted in the administration's inability to create a settled foreign policy agenda.