Talkin’ World War II: Blockades & Subs in the Pacific

Tom Hone recently wrote a marvelous depiction of the Battle of Midway right here on WOTR. As he pointed out, our intrepid pilots and the carrier fleet, supported by great intelligence work, turned the tide in the Pacific.  The U.S. had been forced onto the defensive by Pearl Harbor and by pre-war planning delusions. In fact, however, another World War II campaign may trump the importance of Midway, critical as it was: the effort to choke the Japanese economy through submarine warfare ) This inquiry is particularly relevant to ongoing strategic debates about military strategy in the Pacific put forth by my colleague at National Defense University, Dr. T. X. Hammes and by Commander Jason Glab (“Blockading China: A Guide”) that I will address in my next WOTR article.

There has been an extensive debate over the past year about the Pentagon’s concept for offsetting emerging Anti-Access/Area Denial challenges, the so-called Air-Sea Battle (ASB) concept.  Hammes has developed and espoused an alternative construct called Offshore Control.  This alternative brings our sights up to the strategic level.  Offshore Control is not not without its critics, who question in particular its reliance on at sea interdiction and blockading China’s critical petroleum imports.   But it has garnered wide support inside and outside government., and sparked lively intellectual debate about the plausibility and utility of imposing a blockade on China as well as a related debate on AirSea Battle (ASB).

But blockades and economic warfare in the Pacific are nothing new. A look back at how the strategy was employed against Japan in WWII offers a number of insights for those debating ASB today.

For 40 years before the attack on Pearl Harbor in December 1941, the U.S. Navy had been studying and gaming a war plan for a contest of arms in the Pacific. The entry into World War II presented a chance to demonstrate that those preparations were  strategically sound and operationally feasible. But events would show the plan was not well suited to the character of the conflict that emerged in late 1941.  Significant adaptation was needed.

During the interwar era, the one constant in the Navy’s constantly evolving strategic planning was its focus on countering the empire of Japan – the so-called War Plan Orange.  Much of this planning was driven by the U.S. Navy’s infatuation with Mahan – specifically, his idea of victory by titanic clashes of battleships. American planners recognized that setting the stage for such a clash required a major fleet with a capable naval aviation component, as well as the ability to logistically support a long campaign.  The need for advanced bases to support the Fleet gave play to the development of amphibious capabilities.

The outline of War Plan Orange envisioned three phases:

• In Phase I, the Navy would rush out to the Western Pacific to seize and defend island bases.
• Phase II would involve offensive operations to achieve sea control in the region, and would culminate in battle where “the two battle fleets would meet in a cataclysmic gunnery engagement.”
• The remainder of the war, Phase III, would be “a progressively tightening blockade that would sever Japanese oceanic trade.” The end state of the plan was always a blockade that would choke off Japan’s imports and economy.

Over time, that planning and gaming produced a mental model of how such a war would be fought, and what the Navy’s role would be.  Plan Orange was burned into the corporate memory of the Navy Officer Corps; in the words of Mike Vlahos, it was “genetically encoded” into the U.S. Navy’s thought process.

In the early phases of War Plan Orange, the submarine component of the American fleet played only a limited role. Submarines were auxiliaries or picket ships that would scout ahead of the Fleet and extend its range of observation, a role soon filled by aircraft.   In the culminating phase, submarines were expected to contribute in the naval blockade.  But in the war termination phase – the blockade – submarines got short shrift in games and planning. Only about 5 of 126 War Plan Orange games played with submarines in a material way.  The intense debate over battleships and the evolution of carrier aviation took up more attention.

As a caveat, while the subs got shortchanged in the school’s games, there was plenty of submarine play in the annual exercises.  Even so, a lack of realism and peacetime rules about night training created some false lessons.   The fleet came to believe that subs were easily detected from the air and that they must remain deeply submerged in order to survive.  The force learned to “hide” and provide intelligence more than it learned how to attack.  Attack tactics stressed submerged shootings with sonar from a long distance, diminishing the chances for success.

In the immediate aftermath of Pearl Harbor, the United States reacted by initiating a defensive war of attrition.  Due to its relative weakness and the decision to confront Germany first, the U.S. Navy was not able to implement its much rehearsed War Plan Orange with carrier group thrusts across the Central Pacific searching for a Pacific version of Trafalgar.  Instead, the Navy started by ordering unrestricted submarine warfare against Japan’s sea lines of communications.  The small submarine force was to be the first line of both offense and defense for the U.S. Navy as the war began.

American Navy planners had not totally overlooked unrestricted submarine warfare in 1940 and 1941, but had given little thought to exactly HOW these operations would be carried out.  The Navy had not thought out the necessary components for such a campaign, because it went against   Mahanian principles which stressed decisive surface battles.  The post-war assessment from inside the submarine community was telling: “Neither by training nor indoctrination was the U.S. Submarine Force readied for unrestricted warfare.”  Campaign pressures and operational realities would force the Navy to adapt its plans and way of fighting.

Clay Blair observed that because of its lack of doctrine and working weapons, the U.S. submarine offensive did not truly begin until 1944.  Up until then it “had been a learning period, a time of testing, of weeding out, of fixing defects in weapons, strategy, and tactics, of waiting for sufficient numbers of submarines and workable torpedoes.”  More boats, more aggressive commanders, reliable torpedoes, and better radar/sonar all made their contribution.  By the end autumn of 1944, the period of learning and adaptation was over.  The American sea wolves were numerous, trained, and well-armed.

As the war drew to a close, the role of the submarine as an offensive weapon was evident.  The boats had served as the principal source of attrition for the Japanese economy by targeting Japan’s commerce, especially its oil tanker fleet.  Once the Americans had taken positions in the Philippines, Guam, Midway, Saipan and Okinawa, U.S. forces had cut off the Empire’s energy supply.  Strategically, the war was essentially over. Japanese economic productivity was grinding to a halt.  Japanese tankers were delivering only one tenth of the oil needed for 1944-45.

After the war, there was agreement among Navy leaders that submarines had played a major role in countering Japan. Nimitz, after some distance and reflection in retirement, said: “During the dark, early months of World War II, it was only the tiny American submarine force that held off the Japanese Empire and enabled our fleet to replace their losses and repair their wounds.”  More objectively, speaking well after the war, Admiral “Bull” Halsey observed, “If I had to give credit to the instruments and machines that won us the war in the Pacific, I would rank them in this order; submarines, first, radar second, planes third, and bulldozers fourth.”

The judgment of Navy leaders was validated by post-war government assessments.  As noted in the US Strategic Bombing Survey, the impact of the submarine attrition warfare was strategic in effect:

Instead of the 28,500,000 barrels of oil its leaders expected to import from the Southern Zone in 1944, it imported only 4,975,000 barrels. In 1945 its imports were confined to the few thousand barrels brought in during January and February by single tankers that succeeded in running the blockade….After the battles of early 1945, when Japan lost the Philippines and Okinawa, United States forces sat astride its vital oil life line.  Strategically the war was won.

This history makes one wonder what the U.S. Navy might have achieved if it had invested the same intellectual capital into developing Fleet submarines and working torpedoes that it had in the carrier.  Could the United States have choked off Japan’s trade by the summer of 1943?  Would the battle for Okinawa been so horrific?  Would the war have gone on into the summer of 1945, with the even more horrific consequences that summer brought about?  Could a negotiated peace been achieved that would have precluded the use of nuclear weapons and Russia’s entry into the closing moments of the war?  What other aspects of the Pacific war’s termination would have changed?  That debate may never be conclusive one way or another at the strategic level, but it’s clear that adaptation conferred an advantage at the operational level.  It’s also clear that a generation of planning, wargames, and exercises did not fully pierce the opaqueness of the future.

F. G. Hoffman serves as a Senior Research Fellow at the Institute for National Strategic Studies, National Defense University.  This article is adapted from remarks Mr. Hoffman gave at the recent National Institute for Defense Studies-sponsored history symposium at Tokyo, Japan on Sept. 25, 2013.  These represent his own views and not those of the U.S. government or Department of Defense.