As the United States takes steps toward nuclear arms reduction and urges other countries to follow, an increasing number of nations are employing nuclear power as a major source of energy. While many see utilization of nuclear energy as an important step toward economic development and environmental protection, the expanded use of these technologies may also increase the risk of nuclear proliferation for non-peaceful purposes. The United States and Japan are two of the world’s largest consumers of nuclear energy, and as allies, Japan depends on the United States for protection under its nuclear umbrella. This U.S.-Japan alliance stands at the intersection of civilian and military use of nuclear power. Both countries have a significant stake in the outcome of the debate over the expansion of nuclear energy and the elimination of nuclear arsenals.