Controversial Victory: The “Tanker War” Against Japan, 1942–1944

Abstract

Abstract In the immediate aftermath of the Second World War, the Army Air Corps (soon to be Air Force) provoked controversy by criticizing the Navy’s “tanker war” against Japanese oil, stating that Japan’s collapse might have occurred months if not years sooner had a coordinated submarine campaign against tankers been conducted. For years, submariners pointed to a host of problems as to why enemy oil tankers were not targeted effectively until later in the war, including prewar doctrine, faulty torpedoes and lack of intelligence. The reality – classified until the early 1980s – was that intelligence on the Japanese was so sparse that only through a highly classified signal intelligence effort was enough information derived to target enemy oil. This article will examine the developing and maturing link between signal intelligence and submarines using primary sources declassified in the 1980s. The research will demonstrate that there was no single answer to targeting enemy oil tankers, but only through intense analysis and coordination among multiple Services and agencies were the submarines able to launch their devasting offensive against Japanese oil tankers in late 1943.