Millennium Challenge 2002, the largest-ever joint experiment conducted by the United States, was a major milestone in a concept development process that began in 1999 and continues today. The scale and scope of the experiment was aggressive. But it had to be aggressive, to allow us to assess warfighting concepts using real operational headquarters. This remarkable effort, more than two years in the making, included over 13,500 soldiers, sailors, airmen and marines, operating from 25 locations across the United States. They were placed in an operational environment that integrated live and computer-simulated forces operating in a complex scenario that gave us the most extensive and realistic assessment of our concepts to date. Millennium Challenge 2002 was a congressionally mandated, operational-level, joint experiment that combined live forces with virtual and constructive simulation. MC02 was conducted by the United States Joint Forces Command (USJFCOM) in July and August 2002, and was the culmination of a series of joint experiments. Spanning more than two years, it was designed to assess the ability of a Joint Task Force (JTF) to execute the Rapid Decisive Operations (ROO) war-fighting concept in this decade given a set of enabling and supporting concepts. The hypothesis for the experiment is shown in the box at right. MC02 assessed the ROO enabling concepts of Standing Joint Force Headquarters (SJFHQ), Effects-Based Operations (EBO), and Operational Net Assessment (ON A). The ROO supporting concepts Collaborative Information Environment (CIE), Joint lnteragency Coordination Group (JlACG), Joint Theater Logistics Management (JTLM), and Joint Intelligence, Surveillance and Reconnaissance (JlSR), were also assessed. In addition, the experiment included assessment of 20 joint initiatives, such as the joint fires initiative (1FJ) and Joint Enroute Mission Planning System (Near-term) (JEMPRS-NT) that were not directly in support of ROO, but were focused on improving specific JTF processes.