Australia and New Zealand are not only located in close geographic proximity to one another but also share a similar historical background as former colonies of the British crown. Over the course of the last century, joint military interests brought forces from Australia and New Zealand repeatedly together on various battlefields. Throughout most of the Cold War years, the trans-Tasman defence relationship was primarily defined by the trilateral ANZUS alliance, which also included the United States. This book examines the bilateral defence relationship after 1986, when New Zealand lost its status as an American ally and was subsequently suspended from ANZUS. This study focuses on the most prominent topics that dominated the bilateral defence discourse over the last two decades, including for example the Anzac Frigates Project, Closer Defence Relations as well as regional peacekeeping cooperation. The main aim is to assess the claim that Australia and New Zealand have grown apart rather than together in the post-ANZUS era.