This introductory chapter provides a contextual framework and establishes the key themes that run throughout the book. It starts with an interesting moment that encapsulates the nature of the relationship, in which all delegates heading to the first ANZUS council meeting in August 1952 shared vastly different views about the scope and purpose of the treaty. Zooming back to a macroscopic perspective, the chapter then provides a broader overview of how moments like these were common during this period and briefly addresses the underlying causes of friction in the relationship. Finally, it poses key questions that the book seeks to answer, including why Australia and New Zealand disagreed so regularly about mutual security issues, how US global leadership shaped ANZUS, and the British impact on the trilateral relationship.