During the Cold War, the Japanese Maritime Self-Defense Force (JMSDF) was heavily focused on defending Japan from a Soviet invasion and ensuring sea lines of communications (SLOC) were available for U.S. naval forces in the event of a major conflict. After the Cold War, the JMSDF had to adopt new missions based on the constantly changing threat environment. This thesis assesses how well the JMSDF responded to a variety of threats to Japan during each of the three decades since the end of the Cold War. The main chapters look at the threats Japan faced each decade and then how JMSDF equipment and policy changed as a result of the identified threats. The research suggests that the JMSDF usually falls in the middle of the spectrum and adequately meets defense requirements. It also shows that there were times where the JMSDF was not prepared or was over prepared, but adjustments were made to bring the JMSDF back to the middle ground.This compilation includes a reproduction of the 2019 Worldwide Threat Assessment of the U.S. Intelligence Community.I. Introduction * A. Major Research Question * B. Significance of the Research Question * C. Literature Review * 1. Threats to Japan * 2. Response to Threats * 3. Policy and Equipment * D. Potential Explanations and Hypotheses * E. Research Design * F. Thesis Overview and Draft Chapter Outline * II. History of the JMSDF * A. The Creation of the Japan Maritime Self-Defense Force * B. The JMSDF Through the Cold War * III. The JMSDF in the Post-Cold War Security Environment * A. The New Threat Environment * B. JMSDF Organization and Ships * 1. Cold War Influence on the JMSDF * 2. New Ships for the JMSDF * C. 1990s Policy Changes * 1. The First Post-Cold War Crisis * 2. Moving to Make a Regional Difference * D. Conclusion: The JMSDF'S First Steps in the Post-Cold War World * IV. 2000s JMSDF * A. The Rise of Non-State Threats and the Return of State Based Threats * B. JMSDF Equipment * 1. Ballistic Missile Defense for the JMSDF * 2. Evolution of JMSDF Destroyers * 3. Did Japan Just Build an Aircraft Carrier? * C. JMSDF Policy Changes * 1. Anti-Terrorism * 2. Anti-Piracy and CTF-151 * D. Conclusion: The JMSDF's Role Continues to Expand * V. Current JMSDF (2010 and on) * A. Threats to Japan in the 2010s * 1. North Korea * 2. China and its Growing Maritime Claims * B. JMSDF Ships * 1. JMSDF Destroyer Evolution Continues * 2. Upgrades and Additions to the AEGIS Destroyers * 3. The Izumo Class Helicopter Carriers * C. Policy Changes * 1. Collective Self Defense Allowed * 2. Indian Ocean Deployments * D. Conclusion: Developments Since 2010Since the Imperial Japanese Navy was disbanded in 1945, Japan has gone from not possessing a navy to possessing a well-respected maritime force that maintains capabilities found only among the most advanced navies of the world. The maritime component of the Japan Self-Defense Force (JSDF), the Japanese Maritime Self-Defense Forces (JMSDF), started as a way for Japan to counter regional threats directed at Japan. The JMSDF's mission was, and still is, to prevent threats from reaching the shores of Japan.