The Strategic Studies Institute's XXI Annual Strategy Conference, held at Carlisle Barracks from April 6-8, 2010, addressed the topic of the meaning of war. While it did not seek to produce a definitive answer to questions about the nature and definition of war, it did highlight the crucial questions and their implications, including issues such as whether the cause of war is shifting, whether all forms of organized, politically focused violence constitute war, and the distinction between passive and active war. In the report which follows, Steven Metz and Philip Cuccia of SSI have summarized the presentations and debates at the conference and placed them in their wider intellectual and strategic context,