Within hours of the attack on Pearl Harbor, Roosevelt promulgated a new doctrine: unrestricted submarine warfare against Japan. This meant sinking any warship, merchant ship, or passenger ship in Axis-controlled waters without warning. However, it was not until 1944 that the U.S. Navy began to use its 150 submarines to maximum effect: installing effective onboard radars, replacing commanders who were considered unaggressive, and correcting flaws in torpedoes. In this book I will focus more on the tactical and technical decision-making levels, basing the tasks on examples taken from situations experienced by U.S. submarine crews in World War II. However, I will place their missions within a broader framework of submarine warfare that included the strategic, operational, strategic, and political decision-making levels in order to meet the supposed greatest challenge that the U.S. and the Allies would face during the conflict, which was an amphibious invasion of the Japanese Home Islands. And in the development of this simulation I will use the U-Boot board game from Galápagos Jogos.