A central player in the DoD's organizational approach to communications is the Defense Information Systems Agency (DISA). Today, DISA manages the Defense Information Systems Network (DISN)—a communications network serving as the core connectivity between the various networks of the military services and defense agencies, operating around the world and across the internet with data storage systems, satellite communications, and other advanced data transport capabilities. In addition, DISA plays a critical role in providing security for a wide range of the DoD's computer systems. This CSIS report begins with a discussion of the rapidly evolving environment in which DISA is operating in order to provide context for understanding DISA's operations, DISA's recent changes, and the ways in which DISA's mission is likely to be transformed in the coming years, with a focus on areas that will require careful management by DISA and DoD leadership. It then examines contract data from DISA and related agencies to illustrate how these changes have manifested in DISA's spending and its organizational and operational approach. It concludes with a discussion of the choices confronting policymakers who are considering decisions on DISA's future.