CHAPTER THREE
JAPAN COMES NEARER
Getting lunches and soft drinks, it’s like going on a hike.
Sub-Lieutenant Akira Hiroo
On boarding his midget submarine for Pearl Harbor
When Japan entered the war, the Supreme Commander of the Combined Squadron, Admiral Isoroku Yamamoto, was not keen at first to support the use of midget submarines in the attack on Pearl Harbor. However, he was swayed by the enthusiasm of the personnel directly associated with them and he adopted a plan to use them in the coming operation.
The men selected to crew the midget submarines were small in stature, their average height about 1.52 metres. Most were bachelors, with some exceptions, who showed an aptitude for submarine warfare. Keiu Matsuo was such a man. The son of an elementary school teacher, he graduated from the 66th Term at Kure Naval College in September 1938, after which he was ordered to serve a training period on a destroyer attached to the Combined Fleet. He was promoted to Second-Lieutenant in June 1939, and Lieutenant in November 1940. While attached to the Combined Fleet, he applied for service in the Flying Corps but failed to qualify and was ordered to undergo training for midget submarines. He graduated from the midget submarine school at Kure Naval Dockyard in April 1941 and became one of the first to pilot these experimental submarines.
Matsuo’s intelligence was highly regarded by his peers and superior officers who ear-marked him for greater responsibility. Along with Lieutenants Naoji Iwasa and Saburo Akieda, he became one of the first to propose the use of these craft in a sneak attack, convincing Yamamoto that the crews could be safely recovered after a successful attack.
In addition to these three men, a further eight officers, three warrant officers and 12 petty officers were selected to commence training in midget submarines. Each craft was designed to carry two men – an officer responsible for navigation, speed, communications and target calculations, and a non-commissioned officer responsible for steering, engineering, air purifying and firing of torpedoes.
The first two experimental midget submarines were cigar-shaped with a conning tower to house the periscope. The success of these two craft resulted in another 41 vessels being built and powered by 600hp electric motors. However, they had no generators and so the batteries had to be removed for recharging, either by their carrier vessels or in a dockyard. The midget submarines used at Pearl Harbor were 23.7 metres in length, 1.8 metres in diameter and weighed 46 tonnes. Each had a crew of two. Although experimental in design, they were advanced for their time. For short periods, they could run at 24 knots on the surface and 19 knots submerged, but their endurance was greatly reduced to only 55 minutes. At a submerged speed of 4 knots, however, the midgets had an effective range of 100 miles or an endurance of 25 hours. Each carried two 18-inch torpedoes mounted one above the other, and a scuttling charge to avoid capture. The size of each torpedo warhead approximated 350 kilograms of explosive. These craft were completed only months before the Pearl Harbor attack, allowing little time for crew training.
First sea trials commenced in the Seto Inland Sea. During the ensuing months, extensive workups and exercises were carried out to bring the midget submarines and their crews to a high level of efficiency. The seaplane carriers Chiyoda and Nisshin were speedily converted to carry 12 midget submarines each. These two vessels transported the midget submarines to their operational exercise areas and their callsigns were altered to disguise their real purpose.
It was soon realised that these vessels would have to transport the midget submarines to within about 30 miles of a target area. This, of course, was undesirable, as the seaplane carriers would be detected by enemy patrols, even under the cover of darkness. Considerable thought was directed towards employing the craft in fleet-against-fleet operations instead, but this idea was also abandoned when it was decided that they still lacked a suitable vehicle to carry them. Naval experts then considered transporting the craft mounted on the rear deck of a larger submarine. Carrying the midget submarines in this fashion was a brilliant concept as it would allow a carrier submarine to transport its ward to the mouth of a harbour while submerged. Then, when night fell, it could surface to release the craft, almost within sight of the target. Subsequently, the “I-16 class” submarines were selected to undergo modifications to allow the craft to be clamped to their decks.
On one occasion during training exercises, while learning how to dive under anti-submarine nets, one of the midget submarines failed to return. Piloted by Lieutenant Matsuo with Lieutenant Teiji Yamaki as co-pilot, the craft suddenly stopped when the forward part became trapped in mud. Matsuo gave the order to blow the torpedo tubes, but it was unsuccessful in freeing the craft. Yamaki recounted many years after the war that he suggested the pressure should not be wasted but released slowly, and Matsuo immediately accepted the idea.
So we stopped the blowing and decided to await the rescue ship. Although this was my idea to wait, the acceptance of this advice showed Matsuo’s calm and he never over-reacted to this situation.
Both Matsuo and Yamaki conserved their energy and, over four hours later, bubbles were sighted by Chiyoda and the midget submarine was recovered.
Yamaki described Matsuo as a very enthusiastic officer and when there was no training, he spent his time practising kendo and judo with Lieutenants Naoji Iwasa and Kenshi Chuma, whom he had befriended during training.
Matsuo had a sense of humour and from time to time we visited a small island in the middle of the Seto Inland Sea when there was no training. We collected a group of boys and girls on this island to sing traditional songs and pray together. These three men were just ordinary navy officers … If there was an exceptional factor, it was Matsuo’s mother who was a school teacher and a poetess who composed many poems about her son.
To maintain the secrecy over the midget submarine operations, the codename “Ko-Mark” was adopted when describing the craft. They were also referred to as “SSBs”, “hanger-sheaths”, or simply “sheaths”. The deception was so successful in concealing their true identity and purpose that Captain Shojiro Iura, who served as the Naval Staff Officer of the Submarine Fleet for the coming Pearl Harbor operation, was unaware what was going on. The masquerade continued until September 1941 when plans for the Pearl Harbor attack were revealed to Chief Staff Officers and Commanders at the Tokyo Naval College.
In mid-October, Matsuo’s training exercises were interrupted when he was assigned to special espionage duty in Hawaii. This interruption prevented him taking part as a crewman in the coming operation. Matsuo arrived in Honolulu on 5 November aboard the ocean liner, Taiyo Maru, listed on the ship’s passenger list as a doctor. While in Hawaii, he met with Takeo Yoshikawa, the local spymaster, who drew maps of Pearl Harbor and provided information about the navigation markers leading into the harbour, the position of the anti-submarine net, and the location of ships. Matsuo returned to Japan on 15 November where he submitted his report to the General Staff.
Meanwhile, on 23 October 1941, the captain of I-22, Commander Kiyoi Ageta, received orders to proceed to Kure Naval Base to undergo modifications to his boat. Similar orders were received by four other I-16-class submarines. Ageta secured the submarine alongside the naval arsenal where it was swamped with a team of workmen who began to demolish the rear deck. The following night, under a shroud of mystery, a midget submarine was loaded on to the rear deck, followed some days later by Lieutenant Naoji Iwasa and Petty Officer Naokichi Sasaki who were to operate the craft.
Captain Hankyu Sasaki, the Commander of the First Submarine Squadron, was chosen to lead the midget submarine attack on Pearl Harbor. The squadron consisted of – I-16, I-18, I-20, I-22 and I-24. Sasaki flew his flag in I-22. Soon after Matsuo’s return from Hawaii, he summoned his commanders to Kure where he revealed their part in the Pearl Harbor operation. In the early evening of 18 November, the First Submarine Squadron left Kure Naval Base with midget submarines strapped to their decks. Matsuo joined his friend Iwase in I-22, disappointed he would not take part in the coming attack. After exiting the narrows of the Inland Sea, the squadron fanned out at 20-mile intervals, travelling over the surface until they reached the American-controlled Wake Islands. They then submerged during the day and travelled over the surface at night. The squadron maintained radio silence throughout the voyage.
Soon after departing Kure, Commander Ageta informed his crew of their destination and the purpose of their mission, which was met with great excitement. During the voyage, the midget submarine crews checked and re-checked their equipment and studied detailed charts of Pearl Harbor and the surrounding waters to develop their attack plans.
On 26 November, Captain Sasaki received a radio transmission from the Naval Staff Officer of the Submarine Fleet for the Pearl Harbor operation announcing that negotiations with the United States were now hopeless. On 2 December, he received another communication confirming that the attack was scheduled for 7 December, Hawaiian time. Sasaki received a final report some days later giving the disposition of American naval vessels at Pearl Harbor, which included eight battleships, but no aircraft carriers.
As the First Submarine Squadron advanced on Hawaii, weather and sea conditions deteriorated, making maintenance and last minute work on the midget submarines difficult. Charging batteries, “topping-up with air”, and “lining-up” the torpedoes had to be carried out in difficult conditions because the submarine decks were usually awash. The squadron finally arrived 5 to 10 miles off Pearl Harbor on the night of 6 December. In addition to the five midget submarine carriers, another 22 Japanese submarines took up position in the waters around Oahu. All five midget craft were launched before the planned aerial attack so they would be in position to commence the attack in conjunction with the air strike.
Although Lieutenant Iwasa was the senior officer, each craft operated independently. The original orders were specific. The midget submarines were to lie on the harbour floor during the air strike, then attack the surviving capital ships on the night of 7 December and escape. However, Iwasa asked permission to launch his attack immediately after the air strike instead of waiting for night, and Admiral Yamamoto agreed to his request.
In preparation for the attack, Iwasa and his crewman Petty Officer Naokicki Sasaki, cleaned their bodies with alcohol and sprayed perfume on their underclothes before changing into new uniforms. Matsuo wished his friend good luck and, realising Iwasa had no ceremonial sword, presented him with his own. Iwasa entered the craft first followed by Petty Officer Sasaki who closed and secured the small conning-tower hatch behind him. A few minutes later Iwasa reported everything was in readiness and Commander Ageta gave the order to cut the phone cable and to release the straps holding the midget to the carrier submarine’s deck. I-22 then submerged to send the midget submarine on its way.
Similar procedures were carried out on the other carrier submarines. The first midget submarine was launched from I-16 at midnight, manned by Sub-lieutenant Masaharu Yokoyama and Petty Officer Sadashi Uyeda. A 1:16 am, I-22 released her craft crewed by Iwasa and Petty Officer Sasaki, followed by the midget from I-18 at 2:15 am and manned by Sub-Lieutenant Shigemi Furuno and Petty Officer Kunhan Yokoyama. At 2:57 pm, the fourth midget submarine was launched from I-20, crewed by Sub-Lieutenant Akira Hiroo and Petty Officer Yoshio Katayama. As Hiroo boarded his special purpose submarine he was reported to say with a smile, “Getting lunches and soft drinks, it’s like going on a hike”. Last to leave its carrier submarine was the midget from I-24 at 3:33 pm. Crewed by Sub-Lieutenant Kazuo Sakamaki and Petty Officer Kiyoshi Inagaki, the craft’s departure had been delayed by a faulty gyro compass. The torpedo officer aboard I-24, Lieutenant-Commander Mochitsura Hashimoto, records this incident in his book, Sunk:
It was decided to go ahead without the gyro at 1:00 am [5:30 am Hawaiian time]. The officer commanding the midget went calmly up to the bridge to make his final report and then took his place in the midget. The parent submarine dived, the securing clamps were cast off, and the midget was off to the Pearl Harbor entrance.
Sakamaki’s midget submarine immediately turned somersault after leaving I-24. Many years after the war, he recounted how he could only control the steering by increasing speed and relying on the moonlight to advance towards the harbour entrance. When he put the helm up, the submarine floated rapidly to the surface, and when the helm was put down the craft continued to descend, even after the helm was returned to a neutral position. To maintain any sort of trim, Inagaki, a former engine driver, had to struggle with shifting ballast deposited on the bottom of the submarine from front to the rear, and vice versa, and both crewmen suffered severe pain in their eyes and throats caused by gas generated from spilled sulphuric acid contained in the secondary battery compartment.
One of the fears of the attack planners was that the presence of the submarines would give away the Japanese intent. The fear was justified; however, US forces did not understand the significance of sighting a submarine within the Pearl Harbor defensive zone until too late. The first submarine was sighted at 3:42 am by the minesweeper USS Condor 1-3/4 miles south of the Pearl Harbor entrance buoys. The minesweeper sighted a periscope and notified by blinker light the night patrol destroyer USS Ward, whose commander, Captain William Outerbridge, searched without success until 4:45 am. The next sighting came an hour later when USS Antares, towing a target into the harbour, spotted a submarine following them in. The submarine’s conning tower was fully exposed. A Navy Catalina flying boat dropped “smoke pots” in the vicinity at 6:33 am, giving the night patrol destroyer an approximate location. Four minutes later Ward spotted the midget behind the Antares making a run for the harbour. Captain Outerbridge made a decision in just three minutes to attack. Sounding general quarters at 6:40 am, the aging destroyer’s engines surged full ahead as the gun crews loaded the deck guns. No. 1 gun opened fire at 6:45 am and missed; immediately No. 3 gun fired, hitting the submarine at the base of the conning tower. The submarine heeled to starboard and slowed. The destroyer depth-charged the midget submarine still on the surface before it disappeared for the last time. At 6:54 am, Captain Outerbridge sent a coded message to the naval authorities in Pearl Harbor reporting the destroyer had sunk a submarine off the harbour entrance, but because of delays in decoding, the duty officer did not receive the message until almost 20 minutes later. The decoded report didn’t reach the Commander-in-Chief of the Pacific Fleet, Admiral H. E. Kimmel, until shortly before the air attack had begun at 7:58 am.
At 8:17 am, a second midget submarine was spotted by the destroyer, USS Helm, hung up on the starboard side of the channel entrance. The submarine submerged but immediately popped up again. The Helm fired on the submarine before it submerged again and slipped away.
This craft was crewed by Sub-Lieutenant Sakamaki and Petty Officer Inagaki who were still experiencing gyro compass problems. After many vicissitudes, Sakamaki and Inagaki made a further attempt to enter the harbour, but the gyro compass continued to play tricks and the craft ran aground twice, eventually stranding on a coral reef 200 yards from the beach. Unable to complete his mission, and overcome by foul gas, Sakamaki lit the demolition charge before jumping into the sea. However, the fuse sputtered out and he survived to reach the beach. The body of Inagaki washed ashore some days later, his remains showing evidence that he had died from a gunshot wound to the head.
At 8:30 am, a third midget submarine, commanded by Lieutenant Iwase and Petty Officer Sasaki, was sighted four miles inside Pearl Harbor by the seaplane tender USS Curtiss. The Curtiss fired at the submarine and scored a hit on the conning tower before it submerged and fired a torpedo at the seaplane tender that missed. The destroyer, USS Monaghan, also spotted the submarine and ran at full speed toward it in an attempt to ram, striking a glancing blow as a second torpedo passed harmlessly beneath the destroyer and exploded on the bank at Ford Island. Monaghan dropped two depth charges, which finished off the submarine.
The fate of a fourth midget didn’t become known until 1960 when it was discovered in 75 feet of water off the harbour entrance, her torpedoes still intact but her crew missing.
The whereabouts of the fifth craft still remains a mystery although recent studies of Pearl Harbor attack photographs have led some historians to believe that it was in place off “Battleship Row” as the Japanese torpedo planes came in, and may have fired its torpedoes at USS Oklahoma or USS West Virginia.
In 1993, Commander John Rodgaard, US Naval Reserve (Retired), a senior image analyst at Autometric, Inc., met Dan Martinez, an historian at the National Park Service’s USS Arizona Memorial, and Burl Burlingame, a noted Pearl Harbor historian and local journalist. Martinez showed a copy of what many consider to be one of the twentieth century’s most dramatic photographs. It was taken from a Japanese Nakajima B5N2 “Kate” torpedo bomber during the first attack wave. Martinez saw something intriguing in the photograph and asked Rodgaard if he could determine whether a tiny object in the photograph was one of the Japanese midget submarines. An enlargement of the area in question revealed the presence of a black, rectangular object sitting atop a dark linear structure, followed by “rooster tail” plumes. The analysis determined the image to be a midget submarine, its conning tower and contra-rotating propellers exposed by the concussion of a torpedo hit on the battleship West Virginia.
The photographic evidence indicates the fifth midget submarine had successfully penetrated Pearl Harbor and positioned herself in the south-east loch where she waited to launch her torpedoes at the capital ships on Battleship Row. These ships were identified as the Oklahoma and West Virginia. At 8:03 am, soon after the aerial strike began, the midget fired her first torpedo at the West Virginia, then turned to port and fired her second torpedo. With her second torpedo heading toward the Oklahoma, the midget increased speed and began her run toward the harbour entrance to escape.
Pearl Harbor attack, 7 December 1941 - The first wave of torpedo planes attack “Battleship Row”, seen from a Japanese aircraft. Ships are, from lower left to right: Nevada with flag raised at stern; Arizona with Vestal outboard; Tennessee with West Virginia outboard; Maryland with Oklahoma outboard; Neosho and California. West Virginia, Oklahoma and California have been torpedoed, as marked by ripples and spreading oil, and the first two are listing to port. Torpedo drop splashes and running tracks are visible at left and centre. White smoke in the distance is from Hickam Field. Grey smoke in the centre middle distance is from the torpedoed USS Helena, at the Navy Yard’s 1010 dock. Japanese writing in lower right states that the image was reproduced by authorisation of the Navy Ministry.
While making her escape, the midget was struck by a series of concussion waves. Rodgaard concluded that because of a loss of trim owing to the release of her torpedoes, the effects of her speed, and the oncoming concussions from aerial torpedoes that had struck their targets, that the midget broached the surface when she was buffeted by the cavitation effects generated by the underwater explosions, exposing the midget’s rudder and contra-rotating propellers and causing “rooster tail” sprays to form. This craft was the midget launched from I-16 crewed by Sub-lieutenant Yokoyama and Petty Officer Uyeda.
After the attack, Captain Sasaki assembled his submarine squadron within sight of each other, seven miles off Lanai Island, about 70 miles south-east of Pearl Harbor, and continued to wait for the midget submarines throughout the night. At 22:41 pm, I-16 received a radio message from Sub-lieutenant Yokoyama reporting: “We succeeded in the surprise.” Following this there was a lull until 1:11 am on 8 December when I-16 heard from Yokoyama once again, the midget’s batteries now completely exhausted: “We cannot sail anymore.” After this there was silence. At dawn, Captain Sasaki ordered his squadron to submerge for the day, out of sight until the following night when they would assemble again at the recovery point. After several nights, he gave the order to abandon the wait and for his force to make their way independently to Kwajalein in the Marshall Islands.
The combined air and underwater attack on Pearl Harbor lasted for less than two hours after which it was realised that the American Navy and Army had suffered 3,435 casualties and the loss of five battleships (including the Oklahoma and West Virginia), three destroyers, three light cruisers and a number of smaller vessels. One hundred and eighty-eight aircraft were lost or severely damaged. The carefully planned attack resulted in the loss for Japan of 29 aircraft from a force of 353 launched, and all five midget submarines. By a stroke of luck, not one of the Western Pacific Fleet’s three aircraft carriers was in Pearl Harbor that day. They, and the undamaged American submarine force, soon launched offensive operations into the Western Pacific.
According to American historian Gordon W. Prange, the Japanese Navy concluded that at least three midget submarines had penetrated Pearl Harbor and, after the air raid, had inflicted severe damage, including the destruction of a capital ship. The word quickly spread that the midget submarines had sunk the US battleship Arizona. The Japanese Navy released this to the press in the spring of 1942 and the midget submariners were venerated as veritable gods, to the resentment of the fliers, who knew exactly when and under what circumstances the Arizona had exploded.
When I-22 arrived at Kwajalein following the Pearl Harbor attack, Lieutenant Matsuo transferred to I-16 for the return voyage to Japan where he went to work gathering information from other submarine commanders and looking for ways to improve the performance of the midget submarines. Although none of the crews returned, those associated with the midget submarines, and the crews themselves, insisted that after certain modifications, intensive crew training, and at a location where enemy defences were slacker than Pearl Harbor, that it would be possible to conduct a successful attack and recover the crews. This view was finally adopted by Command Headquarters of the Combined Squadron on 16 December 1941 and preparations for a second midget submarine operation began.
Admiral Yamamoto recognised that a great deal of study and many preparatory exercises would be required if a second attack were to be successful. Even then, he articulated doubts as to whether the crews could be recovered safely. Still, he agreed to proceed with the modifications and crew training.
The approval to go ahead with a second midget submarine operation was met with considerable enthusiasm by those associated with the craft and modifications began. The inability to communicate between the parent submarine and the midget after submerging was recognised as a major problem. Another was that the carrier submarine had to surface and the crew had to walk to the rear deck before transferring to the craft. Not only was this method undesirable at locations where rigid enemy defences were employed, but was also impractical for conducting routine maintenance and service. Subsequently, modifications to allow the crew to transfer while submerged were made by adding a “traffic sheath” (hatchway) that connected the midget to its parent submarine. The lugs securing the craft to the carrier submarine were made detachable from inside the midget submarine.
Work was also done to improve the gyro compass, and an eye glass on each side of the conning tower assisted the pilot when leaving or rejoining the carrier submarine. However, the craft could not be controlled from the conning tower, as the steering gear was located in the control room below. An addition to the midget submarines was a nose guard. The net cutting apparatus used in the Pearl Harbor midgets were replaced with vertical fin cutters with a tensioning wire to the conning tower, which was faired over with steel guards. The tensioning wire then continued to the tail fin. The new modifications were designed to allow the craft to nose under boom net defences. Additional skew strengthening rods were welded to the cage-like structure around the propellers to give additional protection against fouling nets when the contra-revolving propellers were going astern.
The modified midget submarines included a single ballast tank of 52 cubic feet capacity situated in the bow. The ballast tank served to stabilise the craft once the torpedoes were fired to prevent the midget submarine bobbing to the surface. However, the fundamental problem of being unable to recharge the midgets’ batteries still remained. Due to wartime scarcity, the Navy Department would not fit a generator into the craft. Thus, their operational radius remained the same – 100 miles at 4 knots.
The most advanced of the refitted craft was 24 metres, slightly longer than its Pearl Harbor counterpart, fabricated in three sections and bolted together. The modified craft were fitted with two self-demolition charges, one located forward and the other in the control compartment amidship. They were able to operate at a maximum depth of 300 feet, but capable of lying on the ocean bottom at much greater depths. They could remain submerged for at least 12 hours and were able to operate in any harbour for up to seven days, provided they could lay hidden somewhere on the surface during the night in order to ventilate. However, they were still difficult to steer in a horizontal direction, and they lacked a suitable hydrophone to enable the crew to detect approaching vessels.
During the modification period, Admiral Yamamoto made an inspection of the training base at Kure where he gave the crews encouraging words. Plans were now drawn up to use them in Japan’s intended southward advance.
As a preliminary to the planned operation in Australian waters, I-25 was ordered to sail from the Marshall Islands and carry out reconnaissance flights in eastern Australian waters. She was equipped with a small one-man seaplane with a three-hour operating duration. The seaplane carried out a daring reconnaissance flight over Sydney on 17 February 1942, taking photographs of Cockatoo Island and Garden Island dockyards. Undetected by Sydney defences, the pilot and observer successfully rejoined the carrier submarine waiting off the coast. The submarine then proceeded south and conducted flights over Melbourne on 26 With the exception of the spy flight over Melbourne, these flights went undetected and gives some idea of the preparedness of Australian defences at the time. Continuing her astonishing progress, I-25’s seaplane flew reconnaissance flights over Suva and later Pago Pago in American Samoa before turning north to make her report. This same seaplane later flew reconnaissance flights over the Midway Islands prior to that historic naval battle.
By mid-March 1942 there were two main factors influencing the strategy for a southward advance. The Japanese had obtained information that considerable forces had been positioned in the Indian Ocean. Although the war in waters north of Australia had calmed down, sea traffic in the Indian Ocean was still active and formed a supply line from Britain to the Middle East via the African east coast. The other important factor was the effectiveness of the United States Navy. While initially damaged at Pearl Harbor, it was starting to function effectively out of Hawaiian and South Pacific bases.
The Japanese Planning Staff favoured an advance to Samoa and Fiji to cut Pacific communications and isolate Australia. Since the beginning of February a number of attacks had been carried out on Japanese bases, and it was presumed that the United States was trying to support the Australian forces via Fiji, New Caledonia and New Zealand.
While the Chief of the Operations Division of the Combined Fleet, Captain Kameto Kuroshima, favoured an offensive against Ceylon and the Indian Ocean and a linkup with their German and Italian allies, Yamamoto and his Chief-of-Staff wanted to thrust eastward towards Midway and Hawaii for a final reckoning with the United States’ Pacific Fleet. It was Kuroshima’s suggestion that led the Japanese General Staff to draw up plans for simultaneous midget submarine attacks in the Indian Ocean and South Pacific.
On 10 April, Yamamoto ordered the Eighth Submarine Squadron, under the command of Rear-Admiral Noburu Ishizaki, to collect its midget submarines at Penang, on the west coast of Malaya (now Malaysia), and then proceed to the Indian ocean to locate the largest concentration of naval vessels. The midgets were transported to Penang on the disguised seaplane carrier Nisshin.
The Third Submarine Company, under the command of Captain Hankyu Sasaki, was to first co-operate with the Port Moresby invasion and to then collect its midget submarines from the converted carrier Chiyoda at Queen Carola Harbour in the Solomon Islands. It would then proceed to Australia and New Zealand where reconnaissance flights would be made over enemy ports and harbours to locate the heaviest concentration of Allied naval shipping.
Sasaki’s force originally consisted of four submarines with facilities to carry midget submarines (I-22, I-24, I-27 and I-28), and two boats fitted with seaplanes (I-21 and I-29). Sasaki flew his flag in I-21. Following the Port Moresby invasion, I-21 and I-29 were to reconnoitre Sydney, Noumea and Auckland while the others collected their midget submarines. After ascertaining the position of the enemy’s main vessels, the submarine force would then assemble near that area for a scheduled attack at the end of May, when the moon would be full. The midget submarines would be launched within one hour after sunset, or soon after moonrise, and the crews were to be recovered the following morning. If the crews did not return within the planned time, then the recovery phase would continue for another two nights. Immediately after the attack, an aircraft reconnaissance was to be made to determine the results of the attack.
In mid-April, the Eighth Submarine Squadron and Third Submarine Company left their home bases in Japan and proceeded to the Indian and South Pacific Oceans, respectively. After many months of intensive preparations, the attack was finally underway and confidence and morale was running high. Regardless of the outcome, Australians were about to be shaken into a realisation that war was at their doorstep. 