Japanese missions against Sydney and Sydney Harbor
May 29, 1942–June 8, 1942

May 29, 1942
(IJN) I-21 launches its E14Y Glen seaplane to reconnoiter Sydney Harbor. At 0420, it circles twice over the harbor near where heavy cruiser USS Chicago CA-29 was anchored. First thought to be an American plane, RAAF fighters were sent to intercept, but are unsuccessful. The seaplane returns safely and reports sighting a "battleship" in Sydney Harbor. Captain Sasaki orders his force to prepare to attack Sydney Harbor.

May 30, 1942
(IJN) I-24 arrives off Sydney, moves into position to launch its midget submarine.

May 31, 1942
(IJN) Three Type C1 mother submarines including I-22, I-24 and I-27 launch three Type A midget submarines east of Sydney that enter Sydney Harbor to fire torpedoes at warships.

HA-14 Type A Midget Submarine (M27) launched by I-27 became entangled in the boom net across Sydney Harbor between Chowder Bay to Watsons Bay. Entangled, her occupants scuttled the submarine using the explosive charges at 10:35pm killing both crew members and sinking to the bottom of Sydney Harbor. Afterwards during early June 1942 this midget submarine was salvaged by the Royal Australian Navy (RAN) and the remains of the crew recovered and returned to Japan.

HA-24 Type A Midget Submarine (M24) launched by I-24 entered Sydney Harbor and fired torpedoes at USS Chicago CA-29. They missed, but one hit the barracks ship HMAS Kuttabul, killing 21. This midget submarine were never located until discovered by SCUBA divers in 2006.

HA-21 Type A Midget Submarine (M22) launched by I-22 was spotted attempting to enter Sydney Harbor and destroyed by depth charges before it had fired any torpedoes. The remains of two of the midget submarines are displayed at Australian War Memorial and Australian War Memorial Annex.

June 8, 1942
(IJN) At at2:15am Japanese submarine I-24 fires ten times at 30 second intervals aiming at Sydney Harbor Bridge Sydney. None hit the bridge. Only one shells explodes and demolishes part of a house in the eastern suburbs. The others are duds and cause only minor damage. Although the shelling causes no casualties, but some of Sydney's residents panic and flee the city in fear of a Japanese invasion.