This unit presents students with dilemmas faced by U.S. policymakers with three distinct options for U.S. policy toward Japan. Background readings provide students with information on the U.S. decision to drop the atomic bomb on Japan in 1945. By exploring a spectrum of alternatives, students gain a deeper understanding of the values underlying specific policy recommendations. The readings are divided into: (1) "Total War in the 20th Century"; (2) "The Development of the Atomic Bomb"; (3) "July 1945-The Moment of Decision"; (4) "Policy Options"; and (5) "Epilogue: The Decision and the Consequences." The teacher's resource book contains five day-by-day lesson plans with student activities. The material seeks to go beyond the well-worn question, "Should the atomic bomb have been dropped on Japan?" Rather, the unit allows students to examine primary source materials and background information available to U.S. decision-makers during World War II in mid-1945 to reconstruct both the scientific odyssey that produced the bomb and the debate within the Truman administration on whether the bomb should have been used against Japan. This unit rests on the premise that history is best understood when students wrestle with the same historical forces and policy constraints that shaped the perceptions of decision-makers of the past. In exploring the relationship between science and policy, this unit is designed to promote critical thinking skills through interactive cooperative learning and individual analytical exercises. Skills that are emphasized and reinforced in the lessons include reasoning from cause and effect, recognizing historical patterns and connections, presenting oral and written arguments clearly and convincingly, identifying the interaction between values and political actions, drawing generalizations and hypotheses, and understanding the historical context of past policy decisions. This Choices unit includes student readings, a framework of policy options, suggested lesson plans, and resources for structuring cooperative learning, role-plays, and simulations. (CB)