Aside from defending the homeland, no defense commitment in the post-World War II era has been more important to U.S. decision makers than the defense of Western Europe against a Soviet/Warsaw Pact attack. But from the very beginning of the NATO alliance in 1949, the Alliance's ability to stop a Pact invasion without resort to nuclear weapons has been in doubt. Concern about NATO's conventional defense has increased as U.S. strategic nuclear superiority has declined and was brought to the forefront during the debate on the Intermediate-Range Nuclear Forces Treaty. But before we can come to grips with NATO's problems, we need the tools to evaluate the deficiencies and strengths of the Alliance in war against the Pact. This paper presents one such tool, a simple computer model of a blitzkrieg, and uses it to examine scenarios of a war in Europe.