Detailed evaluation of new defense concepts or proposed advanced combat systems can help illuminate the capabilities and limitations of the proposals. If the proposals involve major changes in how forces are organized, equipped, or operated, special methods of evaluation are likely to be needed. This paper presents one such method, which is described and illustrated for a new concept in defending NATO. The concept, called Distributed Area Defense, involves the use of thousands of small units equipped with direct or indirect fire antitank weapons operating over an extended area of the Federal Republic of Germany. The evaluation method uses a three-dimensional "terrain table," a computer program, and a series of analytic modules developed for a hand calculator to conduct a minute-by-minute play of a hypothetical, two-sided combat situation. Innovative human decisions can be introduced, friendly and enemy actions can be examined in detail, and the interactions between concept, tactics, and technology can be demonstrated.