"Wavescan" is a weekly program for long distance radio hobbyists produced by Dr. Adrian M. Peterson, Coordinator of International Relations for Adventist World Radio. AWR carries the program over many of its stations (including shortwave). Adrian Peterson is a highly regarded DXer and radio historian, and often includes features on radio history in his program. We are reproducing those features below, with Dr. Peterson's permission and assistance.
Wavescan N327, May 31, 2015
Focus on the South Pacific: Submarine Radio in Enemy Waters
One morning back in the middle of last century, the people of Australia awoke to the chilling news that Japanese submarines had successfully entered Sydney Harbour and shelled nearby shipping and shore installations. Three midget submarines were launched from three mother submarines about 6 miles off the entrance to Sydney Harbour, on the eastern coast of the Australian continent. This all happened some 73 years ago, this weekend.
Back on December 16, 1941, the Imperial Japanese Navy with its headquarters in Yokohama began active planning for a concerted attack on a major coastal city somewhere in the South Pacific. The four most likely targets would be: Noumea in New Caledonia, Suva in Fiji, Auckland in New Zealand, and Sydney in Australia. It was planned that six mother submarines would carry four midget submarines and two scout planes into enemy waters in the South Pacific.
Next year, on May 11, 1942, four mother submarines were ordered to proceed to Truk Lagoon in the Caroline Islands where they would take aboard one midget submarine each. However one of the midget submarines exploded on board the mother submarine, and this combined vessel was forced to withdraw from the attack project.
During mid-May, the submarine fleet of five combined vessels cruised south from the Carolines, skirting the Solomon Islands, and down into Australian territorial waters. On the way, one of the submarines fired on a Russian freighter steaming out from Newcastle.
In the early morning of Saturday. May 23 (1942), a float plane from the mother submarine I-29 was launched, and it ventured out on a reconnaissance flight over the Sydney Harbour area. A radar unit at Iron Cove detected the intruder, but the initial report dismissed the flight of this hostile plane, under the impression that it was an American.
Six days later, all five mother submarines rendezvoused some 35 miles out to sea off Sydney Heads, the entrance to Sydney Harbour. Then before dawn on Friday, May 29, another flight plane, this time from submarine I-21, made a final reconnaissance flight over Sydney; and again, it was misidentified as an American plane.
However at 5:07 am, an alarm was finally raised and search planes from the Richmond Air Force base took off in an unsuccessful search for the intruder and its mother submarine. The float plane was damaged on its return to the submarine and scuttled, though the two man crew were not injured.
Then at 5:20 pm on Sunday, May 31 (1942), the first midget submarine M-14 was launched from the mother submarine I-27 at a location just 6 miles outside of the entrance to Sydney Harbour. At 8:01 pm, this midget submarine passed over the magnetic loop lying across the entrance, but it was thought to be just a local boat in the area.
A quarter of an hour later, this midget submarine got caught in an anti-submarine net in which it was mortally entangled. More than two hours later, two navy vessels encountered the entangled submarine and dropped two depth charges that did not explode due to the shallow waters. However, the midget submarine M-14 activated scuttling charges that destroyed the submarine and killed the two man crew.
The second midget submarine M-24 was launched from the mother submarine I-24 and it crossed the magnetic loop at 9:48 pm, 1-3/4 hours behind the first midget. This submarine followed behind the local Manly Ferry and entered the harbour waters undetected.
The M-24 was subsequently detected and fired upon by an American navy vessel, the USS Chicago. After firing a couple of torpedoes, the M-24 turned and left the harbor, crossing out at 1:58 am on the Sunday morning.
At this stage, the M-24 disappeared from history, until it was found accidentally in November 2006 by some scuba divers some three miles off Bungan Head, which is some 25 miles north of Sydney. The M-24 was sitting upright on the sea floor, 180 feet underwater, and it showed several machine gun bullet holes; apparently slow flooding brought this vessel to a standstill.
The third midget submarine M-21, from the mother vessel I-22, entered Sydney Harbour over the loop at 10:50 pm. They were spotted shortly afterwards, and so they quickly exited from the Harbour area. However, this same submarine then re-entered the harbour at 3:01 am, though soon afterwards they were spotted again and attacked and destroyed by a surface vessel, the HMAS Yandra.
By prior arrangement, the three midget submarines were expected to meet their mother ships off Port Hacking, 20 miles south of Sydney. Four of the mother submarines were in a row, east & west, with the fifth a little further south. They waited for two days after the attack in Sydney Harbour, but they waited in vain.
The two midget submarines that were sunk in Sydney Harbour were afterwards raised, and a complete submarine was assembled from the damaged pieces for display purposes. The four dead seamen were cremated with due ceremony and their remains were sent to Japan, first on an English exchange vessel, the City of Canterbury which met the Japanese exchange ship, the navy vessel Kamakura Maru at Lourenco Marques in Portuguese East Africa.
On the radio scene, submarine chatter was heard at the Royal Air Force station in Brisbane when the five submarines were off the coast of Queensland. After the first reconnaissance flight over Sydney, the mother submarine transmitted a radio report to Fleet Headquarters at Kwajelein in the Marianas which was heard in part by the American FRUMEL monitoring station in Melbourne. Then, on May 26 and May 29 radio chatter from Japanese submarines was heard in New Zealand, though not decrypted, and direction finding indicated that they were closing in on Sydney.
When the first midget submarine safely crossed over the magnetic loop into Sydney Harbour, they reported on radio to the two other midget submarines the success of their venture thus far. However, the midget submarines talked to each other on the international distress frequency 500 kHz, and these signals were picked up by the army radio station at Middle Head and reported to the navy.
On the night of June 2, FRUMEL in Melbourne again heard chatter from the five mother submarines waiting off the coast of Port Hacking for the return of the three midget submarines. Five air force planes were sent out to search for the waiting submarines, but found nothing.
Wartime historians state that the midget submarine attack on Sydney Harbour did occasion some damage, and one small ship was sunk with the loss of a score of seamen. However, the greatest impact was psychological, and fear of what might come subsequently gripped Australia for some time.
The events of the midget submarine attack on Sydney Harbour took place at the same time as the newspapers were beginning to print their regular issue for the new day, and consequently, very little coverage of the attack was given in the Monday morning editions. Next day of course, very wide coverage was accorded. Soon after the attacks began, local mediumwave stations began to report what was known of the events soon after they occurred, though little accurate detail was known at the time.
Radio Australia, or Australia Calling as it was in those days, reported the attack on Sydney Harbour, and Radio Tokyo gave glowing reports on what they considered to be the success of the venture. Paris Radio erroneously stated that an American navy cruiser had been sunk, along with two merchantmen; and Rome Radio stated that the Japanese successfully blew up Sydney Harbour.
Australia Calling also broadcast the funeral ceremony for the four submariners, and when the ashes of the men arrived in Japan, Radio Tokyo called their return a chivalrous act by Australia that greatly impresses Japan.