This book describes the history of the relationship between the Japan Maritime Self-Defense Force (JMSDF) and the United States Navy (US Navy). The two navies fought each other fiercely on the seas and in the air during the Pacific War. Each found the other a formidable enemy. Soon after the war, when the Cold War turned hot, they began to work together as allies. Many individual officers and sailors on both sides had mixed feelings about cooperating with their former enemies. Over the years, however, these two navies have gradually built strong ties while conducting countless joint operations at sea. Leaders of the US Navy began to realize that this small maritime force, its actions being restrained by domestic politics as well as constitutional limitations, does its job well and can be fully trusted. The JMSDF found that there was no other navy with which it shares common interests and values to be allied with. Close to seventy years of accumulated shared experiences have transformed an initially timid and unbalanced relationship into one of the most successful navy-to-navy partnership in the world.