Summary: In 1996, the Chairman of the Joint Chiefs of Staff issued a conceptual framework for the military's war fighting. Known as Joint Vision 2010, the document identifies information superiority over the enemy as essential. The Defense Department (DOD) defines information superiority as "the capability to collect, process, and disseminate an uninterrupted flow of information while exploiting or denying an adversary's ability to do the same." DOD believes that information superiority can provide significant advantages over the enemy during a conflict and increase the efficiency of peacetime and wartime operations. However, greater reliance on information systems may also make DOD vulnerable to computer attacks and intrusions, damaging its war-fighting capability. This report evaluates DOD's progress in implementing key information superiority activities. GAO examines DOD's progress in establishing a DOD-wide architecture for the information systems known as Command, Control, Communications, Computers (C4), Intelligence, Surveillance, and Reconnaissance (C4ISR) systems; developing and implementing the Global Command and Control System; and establishing the Joint Tactical Radio System.