“Execute Against Japan‪”‬

On 7 Dec. 1941, the U.S. Navy began unrestricted warfare against Japan, attacking “noncombatant” Japanese merchant ships. The decision violated international law and directly cost the lives of thousands of civilian Japanese sailors as well as possibly hundreds of thousands of Japanese civilians on shore. The conditions for unrestricted warfare were created during the interwar period by impractical naval treaties that did not prohibit armed merchant ships that could easily sink surfaced submarines attempting to conduct search-and-seizure operations. Many U.S. naval officers understood the importance of commerce warfare and they suggested changes like prohibiting armed merchant ships in order to permit legitimate submarine warfare. However, the U.S. Navy’s fleet submarine was designed not as a commerce raider but as a warship that could operate in support of the battle fleet in the Pacific Ocean. Fortunately, the abilities required for such a difficult mission gave U.S. submarines the versatility to shift from naval warfare to commerce warfare when the time came. The decision to conduct unrestricted warfare began to coalesce with the acceptance of Plan Dog as the United States’ national military strategy in December 1940. By late September 1941, Chief of Naval Operations Admiral Harold R. Stark and his Director of War Plans, Rear Admiral Richmond K. Turner, had decided to commence unrestricted warfare almost immediately upon the outbreak of hostilities. They did so with no documented approval from their civilian chain-of-command and in contravention of repeated public statements by President Franklin D. Roosevelt, who urged defense of absolute freedom-of-the-seas. Stark, Turner, and other naval leaders had a number of reasons for conducting unrestricted warfare. Chief among these was a pragmatic strategic objective: to economically strangle Japan by completely cutting off the shipping lanes. The American strategy was also influenced by decades of naval training, as well as culturally inculcated Eurocentricism and racism. Although there were a number of ramifications of U.S. unrestricted warfare, the most important and lasting ramification was the end of previous paradigms of freedom-of-the-seas and the introduction of a new and more pragmatic freedom-of-the-seas that classified merchant sailors as combatants and their cargoes as legitimate military targets. This study is the story of that transition.