The United States submarine Robalo slides spectacularly into the Manitowoc River during her launch ceremony on May 9th 1943. USS Robalo was one of 77 Gato Class ‘fleet submarines’ that formed the backbone of the US Pacific Submarine Fleet during World War II. She was also part of a unique sub-group of ‘Freshwater Submarines’ constructed on the shores of Lake Michigan. Submarines were to prove indisputably the US Navy’s most destructive and efficient fighting machine, depleting not only Japan’s maritime resources but also its military manpower. However, a sizeable number of these, including the Robalo, would pay the highest price.
A submarine with sufficient speed and endurance to work alongside a US battle-fleet had been in development since the end of WWI but it wasn’t until the late 30s that a true prototype came into existence, which set the broad design parameters. The Gatos, which went into production in 1940, came to represent the archetypal fleet submarine. They were just short of 100 metres in length and displaced about 1,500 tonnes. Four diesel engines and double shaft propulsion gave them a maximum surface speed of 21 knots and an endurance of 11,000 nautical miles at 10 knots. They could safely dive to a depth of 300 metres and could remain submerged on battery power for up to 48 hours. The Gatos carried ten torpedo tubes, four of which were in the stern. Surface armament generally consisted of a 3 inch deck-gun, a 40mm bofor, and a 20mm oerlikon cannon. They carried a crew of up to eighty officers and men and could be provisioned for patrols lasting 60 days. The succeeding Balao and Tench Classes differed little from the Gatos, their chief advance being diving depth, which increased to 350 metres.
Responsibility for the design and construction of the Gatos fell initially with the Electric Boat Company. Based in Groton Connecticut, the privately-owned shipyard had built the ‘Holland Boats’ the US Navy’s first operational submarines. However, as the war clouds gathered, the US government looked for other private suppliers to meet the increased demands of Roosevelt’s Naval Expansion Bill. The Manitowoc Shipping Company (MSC) had built a number of small cargo ships during WWI but its location on the Manitowoc River, which drains into Lake Michigan, restricted its activities to smaller vessels such as car-ferries and coastguard cutters. Initially skeptical, company president Charles West eventually consented to build ten Gatos using blueprints and assistance from the Electric Boat Co. These ten would be the first of what were later dubbed the ‘Freshwater Submarines’.
Submarine construction at Manitowoc involved a number of novel challenges. As can be seen above, firstly, the boats had to be side-launched, a procedure never attempted before with such a vessel. Secondly, they had to be transported large distances to the ocean. There were two routes available; one to the Atlantic via the St. Lawrence Seaway, which meant traversing the entire length of four of North America’s Great Lakes; the other to the Gulf of Mexico via the Illinois and Mississippi Rivers. The St. Lawrence route contained a number of inconveniences, not least the challenging lock system of the Welland Canal, which joins Lake Erie to Lake Ontario. The Illinois drains directly into Lake Michigan, so was the preferred route. However, a novel means was needed to convey vessels drawing roughly 4 meters along a river system that was in places only 3 meters deep. The solution was to transport each completed submarine inside a dry dock. A final challenge was recruiting sufficient workers to the shipyard. From a peacetime total of 500, the number of workers eventually rose to 7,000.
The first of the Freshwater Submarines, USS Peto, was commissioned on 21st November 1942, just over six months after her launching – an event spectacularly photographed by Life Magazine – and only 18 months after being laid down. By the time of Robalo’s launching the following spring, a further eight had been commissioned. At the time of her own commissioning the following September, the MSC had begun work on another 16 submarines. These were intended to be of the improved Balao design, but due to technical delays at Groton, the first five were actually constructed as repeat Gatos. By war’s end, a total of 15 Gatos and 13 Balaos had been built at MSC and a contract for a further 17 of the Tench Class had been cancelled. For each of Manitowoc’s Gatos, the US government had paid the company $2,850,000.
The US submarine service was handicapped by a number of issues during the opening phase of the Pacific War. Firstly, with only one Gato, USS Drum, in commission at the time of Pearl Harbour, it had to rely on older and partially obsolete submarines including units of the S-Class, which were slow, single-hulled and not designed for operating in the deep Pacific. Secondly, pre-war US torpedo technology proved to be unreliable, resulting in a large number of duds and misguides. Thirdly, the concept of ‘guerre de course’, or commerce warfare, had not been considered by US naval strategists, who had envisaged the fleet submarine’s primary role as ‘the eyes of the fleet’. Consequently, US submarine commanders lacked the tactical knowledge to respond effectively to US Chief of Naval Operations Admiral Stark’s call to ‘execute unrestricted submarine warfare against Japan’ made immediately after the attack on Pearl Harbour.
Among these problems, the defectiveness of torpedoes was perhaps the most pressing. The US Navy’s standard torpedo, the Mark 14, had significant design flaws. The most serious were its tendency to run deeper than its depth setting, to veer off course, and in rare cases run circular, endangering the very forces that had fired it. There were also concerns about the reliability of the torpedo’s magnetic exploder, which in some cases detonated prematurely and in many others failed to detonate at all.
The ineffectiveness of US torpedoes was most clearly illustrated by the experience of the USS Tinosa. In July 1943, she attacked the Tonan Maru III, one of Japan’s largest merchant ships. Over two days, Tinosa fired all but one of her complement of 16 torpedoes at the target, many of them at point-blank range. Of these 15, only two detonated on contact, the remainder proving to be duds.[1] The US Ordnance Bureau was slow to rectify these issues and even late on in the war, weapons malfunctions persisted, most notably when USS Tang was sunk by her own circular running torpedo, killing most of her crew and resulting in the capture and imprisonment of the war’s most outstanding submarine commander, Dick O’Kane.
Tactics were another major concern. Owing to peacetime training deficiencies, the majority of submarine skippers at the outset of the war had limited experience of live-firing and little practical knowledge of how to conduct commerce-raiding. These commanders generally proved to be too cautious in the battle zone, preferring to remain submerged during daylight hours and rely on sonar rather than pursue more aggressive surface tactics. Many of these cautious commanders were quietly replaced by younger officers who were more able to learn on the job, and more willing to undertake the necessary amount of ‘calculated recklessness’ with their boats and crews.
Fortunately for the Americans, the Japanese Navy had its own deficiencies. Firstly, they did not construct enough specialist anti-submarine warfare (ASW) vessels. This was primarily due to doctrinal reasons; the Japanese warrior code emphasizing attack rather than defense, and the protection of commerce being seen as below taking out the enemy battle-fleet. This ASW shortfall was never fully made up; the navy being forced to rely on captured Dutch vessels and a miscellanea of smaller and poorly- suited craft. Secondly, the Japanese tended to restrict the size of their merchant convoys to single figures, allowing US submarines working in coordinated groups to sink or cripple entire supply trains.[2] Finally, and most fatally, the Japanese high command failed to take sufficient precaution with their signal encryption. As a result, not only was the military’s key codes, known collectively to Americans as ULTRA, successfully deciphered by the Allies soon after Pearl Harbour, but their decryption was not even realized by the Japanese until too late in the war. With such strategic and intelligence deficiencies, US victory at sea became a simple matter of deploying enough submarines in the Pacific.
By the time all of Manitowoc’s Freshwater Gatos had reached the Pacific in early 1944, the US submarine service’s multiple problems had been largely overcome, and their operations against naval and merchant targets were being routinely informed by ULTRA code-breakers. The experiences of these fifteen boats in the Pacific theater were representative of the US submarine service in general during WWII. As a group, they carried out the same range of activities and suffered the same mixed fortunes of war.
Bow Creek to Anatahan 