CHAPTER 3 — EARLY WAR AND LIMITED SUCCESS: PEARL HARBOR THROUGH GUADALCANAL

“Our best course of action is to deliver a knockout blow to the American Fleet at the very start. Then Japan can operate … without fear of effective opposition. We can build up our island defense ring, and strengthen our fleet for the day when the recovered American navy tries to move westward. At that later meeting, with our strength at its peak, we can destroy it completely.” — Admiral Isoroku Yamamoto, I Boat Captain

Faced with the realization that the overall plan to draw the American Fleet out for a decisive battle was unmanageable for the Imperial Japanese Navy at the outset of war, Admiral Yamamoto opted for a knockout blow” to disable the American Fleet thereby allowing the Imperial Japanese Navy to expand unabated. Since a significant part of the “decisive battle plan” relied on the submarine force, the alteration of the plan necessitated an alteration in the employment of the submarines. This left the Imperial Japanese Navy to develop new methods of employment for their advanced vessels on the eve of war.

At the time that the Imperial Japanese Navy made their final preparations to sortie for the attack on Pearl Harbor, the submarine force consisted of sixty-three frontline vessels that included forty-eight I-series large submarines suited to long–range offensive combat operations and fifteen RO-series medium submarines that were more suited to area patrol and defensive operations.{59} These submarines formed seven squadrons. Squadrons 1, 2 and 3 consisted of front-line I-series submarines tasked with attacking American fleet combatants. Besides attack and scouting submarines, each of these squadrons also included submarine fitted out as flagships. Squadrons 4 and 5 included front-line I-series submarines mixed with older vessels. Squadron 6 contained the mine-laying submarines. All three of these squadrons were tasked with operations in support of invasions in the southern Pacific Ocean to seize resources. Squadron 7 consisted of RO-series submarines and older vessels assigned to defense of the Home Islands and the Mandates.

Opening Shots

Thirty submarines were assigned to various roles in the attack on Pearl Harbor with only three directly assigned in support of fleet units. These submarines supported four major tasks during the transit to and attack on Pearl Harbor: Advance Scouting, Carrier Striking Force Protection, American Fleet Containment, and Counter-Attack Defense. I-26 and I-10, constituting the Reconnaissance Unit, conducted scouting missions to the Aleutian Chain and South Pacific Islands, respectively, to attempt to locate units of the American Fleet that might risk the security of the Carrier Striking Force. No significant forces were observed during the reconnaissance patrols and both vessels fell into the containment scheme around Oahu. Three submarines were assigned as protection assets as part of the carrier Striking Force. These three submarines were the only ones to operate in a role similar to one that they had trained for in the years of exercises prior to World War II.{60}

The balance of the submarines fulfilled the requirements of the final two tasks. These submarines positioned around Oahu to form a containment cordon that could be reorganized to provide rear protection to the Carrier Striking Force as it withdrew. Included in this force were five submarines of the Special Attack Group that carried Type A midget submarines that would attempt to enter the harbor and intensify the attack. The majority of submarines assigned to this group suffered from some level of training deficiencies, material issues and inexperience. The members of the midget force were affected in particular. As an example, the I-24 conducted her maiden voyage less than a month before taking part in the Pearl Harbor operation. She only had eight days in port to train and have modifications made to operate as a “midget mother.” In the course of the Pearl Harbor operation, she suffered numerous mechanical failures and was nearly lost at least once.{61}

Following participation in the attack in which no submarine fired a torpedo, and all the midget submarines were lost, the Japanese commanders were determined to increase the effectiveness and involvement of the submarines. On 9 December, I-9 sighted an American aircraft carrier (USS Enterprise) and promptly relayed the position and course information. Adm. Shimizu, commander of the Sixth Fleet, organized the pursuit from his flagship anchored at Kwajalein. In the belief that any surviving vessels would be heading for safety on the West Coast, Adm. Shimizu directed the submarines of the First Submarine Group, combined with the Reconnaissance Unit, to transit east to find and sink the carrier.{62} Two days of pursuit resulted in two failed torpedo attacks and the exposure and sinking of I-70 by Enterprise’s dive-bombers. The poorly organized search led to the loss of the first Japanese submarine and the diversion of numerous submarines from the containment cordon around Pearl Harbor. Adm. Shimizu failed to re-organize the submarines left in the vicinity of Pearl Harbor to fill the gaps created by the departure of the searching group.{63} The cordon was further weakened by the requirement that the “mother” submarines make every effort to recover the midgets, thereby causing them to remain in a small area south of Lanai instead of searching for targets. After over four days of searching for the midgets, the five “mothers” departed for Kwajalein.{64} The disintegration of the cordon allowed the free movement of the American carriers after the attack on Pearl Harbor.

The disorganized effort to find and sink the Enterprise is a prime example of the issues facing the Japanese submarine force. The Sixth Fleet Commander broke the integrity of the cordon for an attempt at sinking a carrier. He skewed his operational plan based on false assumptions (eastward retreat) borne of the discarded prewar strategy. The diversion of forces for the search and midget recovery depleted the cordon force by over 40% with no realignment of forces. Ultimately, his choices restricted the ability of the Japanese submarines to find any combatants, including the carriers. Certainly, the distance of the commander from the area of action hampered his decision-making ability as well. Even though the submarine force learned that their submarines could not keep pace with surface combatants during their pre-war exercises, the pursuit group was still dispatched to attempt the chase using techniques that ultimately led to the loss of I-70. The insistence on attempting to recover the midget submarine (because of the requirement to include midgets in the operation) significantly depleted the combat power available in the area. Further, the midget submarines failed to provide any positive contribution to the overall operation and very nearly exposed the entire operation by their detection prior to the air attack. The midgets also provided the Americans with their first Japanese prisoner of war.

The errors in submarine employment during the attack on Pearl Harbor arose from the insufficient prewar exercises and associated training. As such, the submarines operating in the vicinity of Pearl Harbor did not have sufficient experience in the skills and tactics necessary to maintain the cordon. Similarly, the command elements did not have the necessary experience to organize the cordon and attempt to contain breakouts. The commanders did not have the opportunity to practice reorganization of the cordon or employment of the midget submarines. Based on past exercise failures, the staff did not employ the two command submarines (A Type) to control operations on the scene and instead chose to direct the entire operation from Kwajalein.

Even with the lack of results in the actual attack and the days following Pearl Harbor, the Japanese submarines were not without effect. They were able to sink a small number of ships in the days after Pearl Harbor as well as one each by I-10 and I-26 during their reconnaissance cruises.{65} The limited results rested on the lack of training in independent operations coupled with the insufficient training with actual torpedoes. Strict rules for torpedo employment also u limited the potential of the submarines unnecessarily by restricting the numbers of torpedoes versus target type.{66} The intelligence gains of the submarines in support of the operation surpassed the modest results for sinkings. The operations of I-10 and I-26 verified the freedom of the Carrier Striking Force to transit to the Hawaiian Islands without threat from American detection. Further, these vessels proved the usefulness of the excessive range available to the large Japanese submarines by allowing operations in Hawaiian waters after their long reconnaissance cruises to the North and South Pacific. After the attack, the detection of the Enterprise by the I-9 provided the most solid evidence that carriers had survived the air attack. The I-9 launched its scout plane on 16 December to conduct reconnaissance of Pearl Harbor thereby providing further proof that the carriers were not at Pearl Harbor as well as reporting the extent of the damage from the attack. Thus, the operations of submarines provided intelligence that allowed the Carrier Striking Force to operate with impunity while reporting their results without requiring them to remain in range to conduct their own reconnaissance flights.

While the Sixth Fleet submarines struggled to assert their combat relevance at Pearl Harbor, the submarines of the Third, Fourth and Combined Fleets operated in the Southwest Pacific in support of landing and containment operations. These operations followed the prewar plan for the Southwest Pacific. Squadron 6 submarines laid minefields while Squadron 4 and 5 boats provided support to the landing operations. The operations in the Southwest Pacific more closely aligned with the training provided during the pre-war exercises. The submarines acted as a screen for the transports and a number of vessels formed a picket line to intercept Allied vessels leaving from Singapore to threaten the amphibious operations. Their biggest contribution to the initial landings occurred when the HMS Prince of Wales and HMS Repulse departed Singapore to attack vessels conducting a landing on the Malay Peninsula. The scouting line detected the British vessels which forcing the British to alter course. The scouting line regained contact and continued reporting the position of the vessels. Even though the I-58 failed to score any hits out of five torpedoes expended, the position data was critical to allow Japanese land-based naval air assets to sink the only capital ships operating in the Southwest Pacific.{67} At the conclusion of the initial landings in the Southwest Pacific, submarines failed to provide a large list of sinkings to their Fleet Commanders. Nevertheless, the aim of the war plans was realized as all the landings occurred with minimal interruption. The submarine picket line altered the British operations by removing the cloak of surprise from their counter-invasion operations. Ultimately, they facilitated the destruction of the British capital ships before they could threaten any of the landing operations. The submarines completed their responsibilities without the need of their torpedoes, although the failure of I-58 continued a distressing trend.

Emblematic of the lack of operational experience and preparation in the early stages of the war were the numerous failings of operational security among the submarines. The detection of the midget submarines prior to the air raid on Pearl Harbor risked the compromise of the entire plan even though the midgets were not a significant part of the attack. The haphazard attempt to engage the Enterprise exposed the submarines involved to detection because of the high speed directed for the search. A further example of the lack of operational security stemmed from the desire of the crews to have an impact (and potentially some level of pride and face-saving on the part of the commanders). Upon departure from their patrol stations around the Hawaiian Islands, each submarine would conduct a shore bombardment against various positions. These acts of dubious military value provided significant counter-intelligence to the American forces in the Hawaiian Islands. The Americans quickly learned that the bombardments were an indication of the departure of a submarine from its patrol station. This knowledge allowed the Navy to route military and merchant traffic in response to the movement of Japanese submarines thereby limiting the ability of the Japanese submarines to find and prosecute targets.{68} The significant number of radio transmissions required by the Naval General Staff facilitated the sinking of the I-173. American forces were able to triangulate her position and anticipate her direction of movement to allow the prosecution.{69} As evidenced in these examples, the lack of operational security was at all levels of the submarine force from the strategic planning of the initial attack, to the operational coordination of the Enterprise “chase” to the tactical actions of the individual commanders and crews in the Hawaiian Islands. The depth of the issue is most intriguing when the “key lesson” of the October 1940 exercise is considered. Therefore, even with the concern for security because of this exercise, the force failed to translate the lesson to action.

Moving Forward to Coral Sea and Midway

The breaking of the cordon around Pearl Harbor and failed attacks on the Enterprise led to the transfer of nine submarines to the American West Coast in an attempt to cut off supplies and reinforcements to Pearl Harbor to prolong the time required to restore the American naval forces in the Pacific.{70} While the underlying idea was sound, the execution lacked the mass required to complete the task. The division of the forces between the American West Coast cordon, the Hawaii Island cordon and the Carrier Striking Force rearguard left insufficient forces in each cordon to control the area. The disposition of forces also reduced the on-station time of the blockading assets due to the time needed for the advancing and return transits.

An analysis of the operational impact of the transfer of forces to the West Coast will be examined using the example of I-15. The I-15, a B Type scouting submarine, had a 14,000 nm cruising range at 16kts on the surface. Departing Yokosuka on 21 November, she arrived off Oahu on 6 December (4000 nm) where she conducted operations until assigned to assist in the hunt of Enterprise on 9 December. After Adm Shimizu ordered the chase abandoned, I-15 received orders to the West Coast where she arrived on 17 December (2600 nm). Eight days of operations culminated on 25 December with direction to return to Kwajalein. I-15 pulled into Kwajalein on 15 January (5000 nm).{71} Therefore, in 55 days of operations, I-15 traveled well over 11,000 nm just in the major transits that she completed irrespective of the search distances while operating in her cordon role. In those 55 days, she spent only 11 days in the cordon operations expected to destroy warships that survived the initial Pearl Harbor attack and cut off replenishment and reinforcements to the islands. Based on the 2800 nm distance from Pearl Harbor to Kwajalein, the transit would have taken approximately 12 days. Had I-15 stayed in the Hawaiian Islands, she could have maintained her station for at least 26 days prior to departing for Kwajalein. This significantly reduced the effectiveness of the submarines by both increasing the amount of area they had to cover and decreasing the amount of time they could patrol it.

While the manner of employment of the submarines did not yield the impressive results that the Naval General staff desired, it did highlight the long reach of the A, B, and C Type submarines that the Japanese had built. The greater than 11,000 nm transits by I-15 and her six consorts (who all also participated in a couple days of high speed operations attempting to intercept Enterprise) combined with the long reconnaissance patrols by I-10 and I-26 showed the inherent possibilities available to the Japanese submarine force due to their long range. Operating out of Kwajalein, a submarine of the newest type (A, B, or C) could have patrolled along the coast near San Diego for almost 30 days to attack coastal traffic. Three submarines could have maintained a near continuous presence of one submarine on the coast. This same submarine could have patrolled Hawaiian waters for almost 50 days when basing out of Kwajalein. Subsequently, two submarines could have provided continuous presence in the vicinity of the Hawaiian Islands.

Prelude to Midway

Preceding the large scale operation at Midway, the Japanese Navy withdrew the majority of its submarines from the vicinity of the Hawaiian Islands and the West Coast to undergo refit at home.{72} The operational pause was necessary for surface, subsurface and air assets to rest personnel, repair equipment and replenish for follow-on operations. The stunning success of the initial Japanese attacks in early 1942 provided the opportunity to consolidate their equipment and regroup as insufficient assets were available to maintain the offensive pressure continuously. At the conclusion of the refit, the submarine force was reorganized to enhance its operational impact. Part of the reorganization was due to a change in the tactical focus of the submarine force. Submarines were expected to attack merchants and interdict supply lines vice focusing on warships. This was a significant change to the tactical focus of the submarine force in the spring of 1942. This change in tactics did not alter the strategic goal of generating a “decisive battle” to eliminate the American fleet.{73}

Prior to the refit period, in February of 1942, seven submarines were detached from the 30 vessels conducting war patrols to participate in the K-Operation. This operation used submarines to act as refueling, navigation and weather reconnaissance support to an attack on Pearl Harbor by two Japanese “Emily” flying boats. These submarines were removed from their patrol duties for almost a month and ultimately suffered the loss of I-23. As she was the weather reconnaissance unit in the plan, the flying boats did not know about the excessive cloud cover over the harbor and were unable to drop their bombs on worthwhile military targets. One set of bombs landed in the ocean while the second struck civilian housing miles from the naval base.{74} Ultimately, the divergence of nearly a quarter of the available patrol assets from their cordon areas for this operation resulted in no sinkings or damage to ships. The operation failed to provide any usable intelligence (due to weather) and based on the scale of aircraft involvement probably would not have realistically caused significant damage to anything but the American psyche. While the psychological impact of another unchallenged attack on Pearl Harbor could have been significant, the effect could have been possible simply by using the scout planes embarked on the patrolling submarines combined with dedicated shore bombardment around Oahu.

In support of the Japanese planned invasion of Port Moresby (Operation MO), the six submarines of Squadron 4 were deployed with the attack force. These six boats were tasked with conducting shaping reconnaissance of the operating area to determine landing sites, shipping routes, and enemy activity. In the area assignment of forces, I-21 was arrayed in the best position to locate the American battle force. On May 2, she sighted American warships, but failed to observe any aircraft carriers. Of particular impact in the search, I-21 failed to use her embarked plane for scouting thereby restricting her ability to survey the area. As such, the Japanese force did not identify the position of the aircraft carriers to launch a preemptive attack. In the end, with the American loss of USS Lexington, the Battle of the Coral Sea was a tactical victory for the Japanese, but strategically, the Americans stopped the advance on Port Moresby and stalled further advances in the South Pacific. Additionally, the losses suffered by Yamamoto’s air groups at Coral Sea ensured he would have two less big carriers (Zuikaku and Shokaku) for his upcoming Operation MI against Midway.{75}

Midway

The submarine effort in support of the invasion of Midway consisted of a number of other operations designed to drive the American forces into the “decisive battle” that the Japanese desired. One squadron of submarines (the newly created Squadron 8), consisting of five submarines including a Type A Command boat, was sent to the Indian Ocean while a separate attack force, also of five submarines, was sent to the east coast of Australia. Both units were equipped with A-Type midget submarines and were tasked with conducting attacks on major ports. Outside of these specific attacks, the submarines were expected to roam and attack merchants. Both attack forces employed their scout planes to reconnoiter their respective targets of Diego Suarez (a port in Madagascar) and Sydney Harbor, respectively. Within 24 hours of these scouting flights confirming the presence of warships in the harbors, each attack force launched midget submarine attacks. The attack on Sydney Harbor failed to claim either of the two major combatants in the port, but did destroy a ship being used as a floating hotel” for servicemen. The attack in the Diego Suarez destroyed a tanker and damaged the British battleship HMS Ramillies (removing it from action for almost a year). The Japanese Navy hoped that these harbor attacks coupled with increased submarine operations in more distant areas would drive the American commanders to join in a “decisive battle.”{76}

The dismal results of the Japanese submarine forces at Midway were foreseen in the lackluster planning applied to the operation. Vice Admiral Komatsu, commander of the Sixth (Submarine) Fleet, played little role in the generation of the employment plan. Enamored of Yamamoto’s previous successes, Komatsu considered the result at Midway a foregone conclusion and chose to focus on follow-on operations without questioning the overall plan. The organization of the Midway submarine effort was left to junior staff officers. As a result of the lack of attention from senior staff personnel, details of the submarine cordon plan were left out of the official orders for Operation MI. The lack of focus on the task was not a fault of the submarine staff alone. War games conducted in preparation for Operation MI were little more than rubber stamps for the operation as Yamamoto’s Chief of Staff, Admiral Ugaki (acting as the umpire for the games) frequently overlooked the difficulties in the plan and forced the games to move forward without questions from the underprepared staff that was present.{77}

The submarines assigned to the Midway and Aleutian (AL) Operations had a number of disparate roles. Two submarines conducted a reconnaissance of the Aleutian Islands in advance of the invasion force and then departed for the West Coast. Three submarines assigned to the Aleutian Operation (out of four total) were tasked with supporting the invasion force in its initial actions followed by forming the easternmost scouting line, approximately 1000 miles from the West Coast, to provide early warning in support of the Japanese forces approaching Midway. Squadron 1, consisting of seven submarines, was assigned to follow the invasion force into the Aleutians and ended up being reassigned to the West Coast based on the lack of targets and operational need in the Aleutians. In total, thirteen submarines were committed at some point to the Aleutian phase of the operation with three transitioning to patrol in support of the Midway attack and nine proceeding to the West Coast. One remained in the Aleutians. These boats recorded four merchant sinkings along with the shelling of various coastal areas. None of the American forces at Midway were detected.{78}

The Japanese Navy also dispatched seven submarines from the Midway force to attempt a second K-Operation sortie over Pearl Harbor. I-121 and I-123 were assigned as the refueling assets and encountered American ships in the anchorage at French Frigate Shoals. The operation was called off when the American vessels did not depart after a few days and the Japanese conducted no alternate attempts to scout Pearl Harbor.{79}

In addition to the three submarines forming the easternmost scouting line composed of boats from the Aleutian Operation, two more scouting lines were arrayed in search of American forces. Five submarines from Squadron 3 involved in the K-Operation were assigned to the southeast of French Frigate Shoals to block the southern side of the Hawaiian Island chain. The eight submarines of Squadron 5 were assigned to form a third picket line 900 miles east of Midway to block the northern side of the Hawaiian Island chain. These two lines were expected to be in place by 4 June but in the end the lines were only completed on 6 June. The delays evolved from the operational commitment of the Squadron 3 boats to the failed repeat of the K Operation and the increased maintenance requirements of the older boats assigned to Squadron 5. The Squadron 5 boats were delayed by difficulties during their refits in Japan and subsequent materiel issues requiring repair at Kwajalein prior to departure for Midway. Exacerbating the delayed arrival of the Squadron 5 submarines was failure of Komatsu to inform Yamamoto that the scouting lines were not formed by the time expected.{80} Consequently, the Japanese force had no intelligence about the American aircraft carriers due to the failed K-Operation flight and the incomplete scouting lines. By the time the lines were complete, the American force had passed completely and four Japanese aircraft carriers lay at the bottom of the Pacific Ocean.

When Yamamoto made the decision to abandon the Midway operation, all submarines were shifted to a scouting line 500 miles east of Midway in a final attempt to mitigate the loss of aircraft carriers by sinking the American aircraft carriers. The attempt was abandoned when Yamamoto had the scouting line moved to the 180th Meridian to cover the withdrawal of the remaining Japanese surface forces. This line finally formed completely on 10 June and then was quickly dispatched in another high speed run to the east when the American carriers had finally been located. After the series of line shifts requiring high-speed transits by the boats, the submarines lacked the necessary fuel or speed to overtake the withdrawing American carriers.{81} The unsettled employment of the submarines after the late assembly of the initial scouting lines further degraded their effectiveness in support of the “decisive battle” around Midway.

The lone success of the Japanese submarines at Midway occurred when I-168 sank the American aircraft carrier USS Yorktown. While the overall impact of the sinking cannot be overlooked from the aspect of total aircraft carrier strength in the Pacific, the sinking also provides a prime example of the efficacy of Japanese pre-war individual unit training. Commander Tanabe, commanding officer of I-168, successfully penetrated a screen consisting of five destroyers around Yorktown with an eight hour submerged approach in daylight. His persistence in the approach led to the sinking of Yorktown as well as the destroyer USS Hammann that was providing services to damage control team onboard the already damaged carrier. While the approach was made easier by the slow speed of advance of the Yorktown and her escorts, the experience gained in pre-war exercises prepared Tanabe and his crew for the lengthy approach and follow-on seven hour evasion that made Tanabe a national hero.{82}

The series of coincidences that led to Tanabe’s successful attack give an interesting insight into the vagaries of combat. Material issues onboard I-168 delayed her ability to join her assigned scouting line. Based on this delay, I-168 was assigned to conduct a reconnaissance of Midway and then join in a bombardment of the islands along with a force of four cruisers. During her reconnaissance, she reported increased activity at Midway that should have alerted Yamamoto that the surprise attack had been compromised. Unfortunately for the Japanese, these vital reports were ignored. Based on her modified tasking, I-168 was the only vessel in close proximity to the reported position of Yorktown and able to press an attack.{83}

Zenji Orita, a Japanese submarine captain during World War II, contends that the major failing in the Japanese deployment of the submarines assigned to the Midway force was the failure to array the submarines ahead of the carrier force as done at Pearl Harbor. The Japanese submarines moved in broad scouting lines in advance of the Carrier Striking Force until they reached station around Oahu. At Midway, the submarines were deployed independent of the surface forces and did not effectively search ahead of the force for the American aircraft carriers.{84}

While the general idea that the array of forces was ineffective is true (since no submarines gained contact on the American forces before the battle was over), to simply say a change in disposition of the forces would have altered the battle is disingenuous to the other issues involved. First among the issues is the broad disposition of available forces. Viewing Midway as the possible position of the “decisive battle,” the Japanese Navy committed thirteen submarines to the associated operation in the Aleutians making them unavailable for immediate reassignment to the Midway effort. Further, seven boats were assigned to the failed K-Operation thereby delaying their arrival onto their picket line. This does not even consider the ten submarines assigned to the Indian Ocean and Australian operations as they were ostensibly in support of moving the Americans towards commitment to a “decisive battle” at Midway. Thus thirteen vessels were removed from the vicinity of the “decisive battle” while ten more were committed to questionable operations that failed to influence the American response at Midway.

Second, ten of the submarines assigned to the effort at Midway represented some of the oldest and least capable in the force. The age and poor condition of the eight submarines of Squadron 5 directly contributed to their inability to gain their picket stations prior to the battle. Prior to their inclusion in the Midway plan, all the boats of Squadron 5 had been slated for designation to training and coastal defense duties. The I-121 and I-123, two of the four minelayers of the KRS Type, had their mining equipment removed to install maintenance shops and extra fuel to support the K-Operation thereby negating one of their greatest capabilities. At the same time, the more capable boats of Squadron 2 along with newly built units formed the forces that travelled to the Indian Ocean and Australia thereby reducing the combat capability of the boats assigned to the Midway operation. None of the boats assigned to the Midway force carried scouting airplanes that could have conducted the surveillance of Pearl Harbor in lieu of the failed K-Operation. The addition of submarines with scouting aircraft could have also mitigated the relatively small number of submarines specifically assigned to support the attack.

Finally, the haphazard shifting of the patrol lines exacerbated the problems due to the small number of submarines assigned to the Midway Operation and their overall quality and capability. The disorganized movements negated the ability of the submarines to actually search for the American forces and nullified their ability to go on the offensive when the American warships were located. The shifting of lines opened gaps to allow freedom to the American forces in much the same way that the cordon around Pearl Harbor was rendered ineffective by removing nearly one third of the available submarines for the chase of Enterprise.

Viewed in their entirety, these three issues all have a foundation in the lackadaisical planning conducted by the Naval Staff in the creation of the plan for Operation MI. Based on past successes, the senior commanders chose to focus on operations further in the future. Subsequently, the junior staff left to work out the details did not challenge the plan initially proposed by Yamamoto. The detailed planning and wargaming that made Pearl Harbor successful was not utilized to generate appropriate contingency plans or identify faults. Weaknesses in unit capabilities were not identified. Operation MI was a failure before it began and the submarine force effort in it was almost non-existent.

Guadalcanal and the South Pacific

While the defeat of the Japanese forces at Midway represented a significant shock to the combat power and momentum of the Japanese Navy, the operation at Guadalcanal represented the last opportunity for the Japanese Navy to perform a significant counterstrike against the nascent American counter offensive following Midway. While the operations of the Japanese submarine force at Guadalcanal had little impact on the actual events there, they are the high point of the Japanese effort to sink or damage capital ships. The submarines would account for one aircraft carrier and one cruiser sunk along with a second aircraft carrier and a battleship damaged and removed from operations for months.

At the beginning of American operations near Guadalcanal, only two units of Squadron 7, RO-33 and RO-34, were in close proximity, operating in the Bismarck Sea. I-121, I-122, and I-123, the old minelayers, were dispatched to reinforce the effort. By 24 August, ten more submarines had been diverted to the area from Japan and Australia. The task of the initial submarine forces was to cut the shipping lanes to Guadalcanal, but they failed to have any impact for the first three weeks of the invasion thereby allowing the Americans to grab a vital foothold on the island. In general, the submarines were effective at reporting the positions of naval units but unable to generate the desired sinkings. A further group of reinforcements was sent in by 19 October without significantly impacting the result of the invasion.{85}

The submarines initially formed two scouting lines, one 200 nm northeast of Guadalcanal and a second 150 nm southwest of Guadalcanal. The intention of the lines was to interdict supplies and warships from Hawaii and Australia. On the evening of 24 August, two submarines sighted aircraft carriers and the subsequent reports led to direction to all submarines on the picket lines to intercept. After a day of fruitless searching, the submarines were dispersed back to their picket positions where they would remain until the picket lines were reorganized on 31 August. This reorganization did ultimately place the submarines in a position to conduct a couple critical engagements that will be discussed later. Besides picket duties, submarines were also tasked with seaplane reconnaissance and nuisance raids on neighboring islands.{86} Even with the successes that occurred, the submarines suffered from continuing lines shifts and fruitless chases like the closing days of operations around Midway. This led the submarines into an untenable position of continuously chasing events vice being able to position ahead of American forces.

As at Midway, the employment of submarines at Guadalcanal did lead to some critical successes. On 31 August, Commander Minoru Yokota, commanding officer of the I-26, conducted a screen penetration followed by a 12 hour evasion that resulted in damage to the aircraft carrier USS Saratoga removing her from combat operations until late November. Commander Takaichi Kinashi, commanding officer of I-19, conducted a screen penetration on 15 September that resulted in the sinking of the aircraft carrier USS Wasp, damage to the battleship USS North Carolina and eventual sinking destroyer USS O’Brien. This penetration resulted in 23 warships in range of the I-19’s torpedoes at the same time period as the sinking of the Wasp. On 13 November, Yokota conducted another attack against a force of five warships that resulted in the sinking of the cruiser USS Juneau.{87} These successes again reflect well on the pre-war individual unit skill training exercises. Interesting in the results, was the report of Yokota of the “poor state” of American ASW techniques that would lead to overconfidence by later commanders and higher Japanese casualties.{88} The result of the attacks was to reduce the American fleet to one combat capable aircraft carrier in the Pacific, USS Hornet. Ultimately, the significant advantage produced by these results was not taken advantage of by the Japanese commanders based on trepidation due to the defeat at Midway and lack of intelligence of the American fleet disposition based on the continuous shifting of submarine picket lines.

As the situation on Guadalcanal continued to degrade, the Japanese submarine force resorted to special weapons to attempt to stem the American build-up. Three submarines, I-16, I-20, and I-24, were tasked with operating as mother ships for A-Type midget submarines. They were directed to attack the supply vessels in the vicinity of Guadalcanal landing area with the midgets expected to increase effectiveness in the shallow areas. The series of actions comprising attacks by eight midgets resulted in only one sinking. This effort was the last concerted attempt to target American supply vessels supporting the Guadalcanal operation after 15 November.{89}

The failure of the submarines to provide positive results in the effort to stem the flow of American supplies to their forces on Guadalcanal placed the Japanese Army in a precarious position. The need to reinforce the troops ashore led the submarines to a unique employment: submerged resupply. While the use of submarines for individual supply runs and evacuation missions was a normal event for all major combatants in World War II, the magnitude of the operational scope of the Japanese mogura, or “mole,” operations made them unique step beyond that applied by other countries. On 16 November, all available I-boats were ordered to Rabaul for commencement of supply operations. The I-boats were chosen based on their larger size, and therefore carrying capacity, while the small number of RO-type medium submarines was left to conduct patrols. Submarines involved in supply operations offloaded all of their spare parts and the vast majority of the crew’s rations to make room for ammunition and food for the troops on Guadalcanal. The reload torpedoes and scouting aircraft were removed to make extra storage space in the torpedo rooms and hangar. Deck guns and ammunition were removed to free both space and weight. As the situation worsened, submarines even backhauled and offloaded all of their torpedoes to use the empty torpedo tubes for storage. Thus, the submarines employed in this effort had all of their offensive capability removed. Sixteen submarines joined the operation in the initial thrust with each one capable of providing almost 2 days of supplies in each trip. The effort was considered so critical that Rear Admiral Mito, the commander of the effort, rode I-8, for one of the resupply missions to personally survey the risks involved. At the point the submarine resupply operations were cancelled in February, 1943, over 1100 tons of supplies were delivered to the forces on Guadalcanal and over 2000 wounded soldiers were evacuated. In supporting this failed effort, four submarines were sunk while no American ships were sunk or damaged. Significant in these losses was the destruction of I-1 by the New Zealand patrol craft Kiwi and Moa. She sank in shallow water where American salvage teams were able to retrieve numerous pieces of communication and cipher equipment.{90}

Once the situation of Guadalcanal became improbable for Japanese victory, the submarines suffered employment as rear guard for units assigned to evacuate nearly 12,000 personnel from the island. Because of the ability to base submarines at Rabaul, smaller, shorter ranged RO-series submarines made up a larger part of the submarines assigned to the area. The tasking of the submarines in the area diverged further and further from pre-war training and plans. In early march 1943, RO-101 and RO-103 sortied solely to conduct a rescue mission to pick up survivors of a ravaged Japanese troop convoy. A later deployment of L.-Cdr Orita’s RO-103 had three major tasks listed in the orders to the commander: provide weather reports, conduct air-sea (lifeguard) operations; sink enemy shipping.{91} Japanese submarine operations in the Solomon Islands near Guadalcanal had taken a decided turn to the defensive or worse.

On the surface, the results of Japanese submarines in operations around Guadalcanal appear impressive when viewed against the results at Midway and Pearl Harbor. The submarines sank an aircraft carrier, cruiser, and destroyer as well as damaging an aircraft carrier and a battleship. These successes belied the failure of the submarines to accomplish the desired goal in the waters around Guadalcanal. Only a small number of transports and supply ships supporting the American assault were sunk or damaged. The submarines employed in the Solomons were not able to present a credible threat to the American assault to disrupt the resupply effort.

There were two reasons for the failure of the submarines to achieve meaningful results in the waters around Guadalcanal. First is the shifting of patrol lines in search of targets. While the shifting was fruitful in some respects, the submarines failed to identify and destroy supply vessels before they could discharge their forces and cargo at Guadalcanal and neighboring islands. The shifting of the lines limited the ability of the submarines involved to search their operational areas for supply ships effectively. The submarines also occupied areas where the supply ships would still be protected by warships in less restricted waters vice attacking in the more restricted waters close to the landing beaches.

The second reason for the poor results in the Guadalcanal area was the dilution of the combat strength in the area due to the assignment of the submarines to missions other than interdiction of the American resupply effort. Submarines were reassigned en masse to resupply efforts instead of offensive action. When not assigned to resupply efforts, they were conducting air-sea rescue or weather reporting as well as other mission in lieu of conducting interdiction. The diversion of submarines to alternate missions effectively ended the ability of the Japanese to influence the result at Guadalcanal and simply delayed the inevitable loss of the island.

Operations on the North American West Coast

Sending submarines to the North American West Coast was initially a follow-on action of the diversion of vessels from the Oahu cordon to search for Enterprise following the attack on Pearl Harbor. Seven submarines were joined by I-10 and I-26, the boats that conducted the long scouting missions prior to the Pearl Harbor attack, in patrolling the entire expanse of the American West Coast. All nine submarines reached their assigned patrol areas between 17 and 20 December. The long transit to take station off Pearl Harbor, coupled with the search for Enterprise, depleted the fuel reserves of the vessels patrolling the coast. As such, the members of the patrol lines departed for Kwajalein on 27 December. Most of these boats arrived at Kwajalein on 11 January to end their first war patrol. The Japanese Naval Staff originally intended for the submarines to bombard various targets on Christmas Eve in a coordinated attack. The attack was delayed and ultimately cancelled. The first foray of submarines to the West Coast resulted in approximately 80 hull-days on station and the submarines were responsible for the sinking of five cargo ships and damaging of a further five.{92}

This ten-day period would be the last time that multiple Japanese submarines would be in American coastal waters (excluding the Aleutians) at the same time until June 1942. It would also stand as the first and last major Japanese effort to conduct operations off the West Coast. While late December 1941 would be the period of the most submarines operating off the West Coast, late January through mid-March 1942 would account for the longest period of presence on the coast. I-8 and I-17 would combine to provide a single submarine on the coast for approximately 50 straight days. This period resulted in no sinkings. Of greatest interest during this period of operations was the bombardment of Ellwood, California by the I-17. This marked the first time that the American mainland came under attack since the War of 1812.{93}

Following the patrol of southern California by I-17, the Japanese would organize four more patrols by submarines off the American and Canadian coasts. I-25 and I-26 conducted patrols during June 1942 overlapping for approximately six days but operating in different areas along the coast. While the operation of these two in general did not have a large impact on the war effort, the I-25 would return in September 1942. She used her “GLEN” scout plane to drop incendiary bombs on forestland in Oregon in an attempt to start forest fires and destroy timber. (Unfortunately for the Japanese, heavy rainfall in the weeks prior to the attacks thwarted the plan.) These attacks marked the only time that mainland America suffered aerial bombardment. The final patrol to the West Coast would not occur for two years. I-12 conducted a patrol to the West Coast in October and November of 1944. I-12 would be sunk on return from this patrol.{94}

The choice of targets tempered the dramatic nature of some of these operations. The Japanese Navy Staff did not want to risk retaliatory strikes so they initially cancelled the December bombardments. When bombardments were allowed in later patrols, the submarines were directed to avoid bombarding large population centers such as San Diego and San Francisco. The attacks focused on strategic materials (oil fields in Ellwood and timber in the Oregon forests) instead of popular resolve. The effort, however, did not match the goal as the submarine deck guns had limited range and firepower and the “GLEN” scout plane was only able to carry two small incendiary bombs. The submarines, operating in limited numbers, could not hope to have significant strategic impact by conducting surface and aerial bombardment.{95}

Japanese operations off the American coast stood in stark contrast to the German efforts on the opposite side of America. While the Japanese push to the West Coast was a follow-on element to the Pearl Harbor attack it was not specifically planned until the units were broken off to pursue the Enterprise. Highlighting the failure to plan for contingency operations after Pearl Harbor is the example of the I-26. As one of the original two advance scouts with I-10, the I-26 was the first boat to reach the American West Coast, but the boat departed Japan with only ten torpedoes onboard. Total capacity was seventeen. The torpedoes onboard were older, obsolete models instead of the highly capable Type 95 torpedoes. I-26 was deployed without the ability to conduct an offensive patrol to maximum effect by being provided with a half load of second rate torpedoes. Had detailed consideration been given to follow-on operations, all submarines would have been deployed with full loads of the best weapons available.{96}

The German U-Boat Command, led by Admiral Karl Dönitz, conversely, had developed plans and intent even prior to the entry of the United States into the war. While the Japanese committed nine submarines to their initial effort, the Germans could only muster five Type IX long-range submarines. The significant factor that made the German operation much more successful was the confinement of these limited resources to a smaller geographic area. While the Japanese spread their nine submarines all along the American and Canadian coast, the German submarines intentionally focused between the St Lawrence River and Cape Hatteras.{97}

Once the initial force of Japanese submarines had exhausted their fuel, there were no replacements immediately available to maintain pressure along the coast. The Germans however had three more submarines on station before the original five had to retire. The German U-Boat Command reorganized forces to continue to push assets to the American coast to maintain a constant presence of between six and eight submarines starting in March 1942.{98} The Japanese never attempted to surge a large force of submarines to the West Coast to follow up on the initial nine-boat effort. The Germans continued to push more and more submarines towards the American coast. The German U-Boat Command also responded to changes in the anti-submarine efforts and expanded the area of operations to dilute the available challenge to the U-boat operations. The entire North American eastern coast as well as the Caribbean Sea and Gulf of Mexico were threatened by the U-boats as “Operation Drumbeat” expanded. The Germans further employed mines at significant points on the Canadian and American shorelines as a force multiplier to make up for the smaller than desired number of boats available for operations.{99} While the Allied anti-submarine forces and adoption of convoys in coastal areas ultimately effectively countered the German U-boats off North America, the Germans were able to sink nearly one third of their total tonnage during the war in these operations on the American East Coast.{100} The Japanese never sank more than a small handful of merchants in similar operations.

The dichotomy in the results of the German and Japanese operations is exemplified in the manner of response on each coast to the attacks. The German attacks on the East Coast garnered a contraction of the American forces to the coastline. It also led to a transfer of Allied anti-submarine forces from convoy operations in the Atlantic to support the American effort to secure its coastline. Mine warfare forces were deployed to clear harbor areas. The effort was effective enough to cause the Allies to risk weakening the convoy escort forces to assist the American effort.{101} Conversely, the Japanese effort on the West Coast did little to elicit a widespread military reaction. The lack of results from the initial operation on the West Coast allowed the American coastal artillery teams to maintain a centralized basing arrangement. When the shelling of Ellwood City occurred, the coastal artillery teams took nearly three hours to travel from their base in Goleta to firing positions in the area of the attack. Based on the lack of severity of the attack, the coastal artillery chose to maintain the status quo and not deploy to forward positions. By the time I-17 conducted this shore bombardment in February, the response of the American Civil Defense forces devolved to be nearly non-existent.{102} For their part, the Canadians also had minimal reaction to the attacks. The Canadians enlisted a number of fisherman into the Fisherman’s Navy Reserve and used their fishing vessels as an ad hoc patrol force because the anti-submarine vessels were thought to be more necessary in the Atlantic.{103}

Conclusions from the First Half of the Pacific War

The planned employment of the Japanese submarine force in the early battles of World War II was sound. Unfortunately for the Japanese, the actual use of the submarines was far from acceptable. The failures ranged from lack of patience in maintaining the cordon around Pearl Harbor, to a lackluster commitment of submarines to complete their tasking at Midway to a poor assignment of priorities at Guadalcanal. The Japanese abandoned their original vision of employment of their submarines for a “decisive battle,” but they did not devise a clear alternative. When opportunities were available for the submarines to contribute positively to each of these battles, they were frenetically deployed in search of the “big win” sinking of a capital ship. Even after the Japanese announced a tactical change for the submarines to commerce raiding vice hunting warships, they failed to assign them to areas that threatened the American lines of communication or, when they did, they assigned them to tasks to which they were unsuited instead of interdiction. The haphazard employment of the submarines diluted the combat power of an already small force and then dispersed it to areas of questionable strategic value such as the Indian Ocean and the Aleutian Islands.

Despite the issues with their employment, the Japanese submarines did prove the power of their design by conducting numerous long-range patrols in all areas of the Pacific and Indian Oceans. They were capable of providing forward observation and damage assessment after operations were complete. The commanders further showed the efficacy of their individual training through a number of impressive approaches that resulted in significant sinkings. The threat of their presence even influenced the American operations at Guadalcanal.{104} They showed an ability to adapt to the tasking given to them even though much of it deviated from their pre-war training and experience.

Having lost their initial momentum from the attack on Pearl Harbor, the Japanese submarine force would attempt numerous alterations to equipment and tactics. These changes would range from minor and inconsequential to the massive and extreme.