The Dutch submarine K IX, later commissioned as HMAS K9, was a K VIII-class vessel built for the Royal Netherlands Navy (RNN) in the early twentieth century. She was ordered on 27 June 1917, laid down at the Koninklijke Maatschappij De Schelde shipyard in Vlissingen on 1 March 1919, launched on 23 December 1922, and commissioned into Dutch service on 21 June 1923.
Following her commissioning, K IX was deployed to the Netherlands East Indies (NEI), arriving on 13 May 1924. She served in the region for many years but was out of commission by 1941. As Japanese forces advanced rapidly through Southeast Asia in early 1942, K IX was hastily returned to service in March. After the collapse of Allied defences in the NEI, she escaped to Australia, arriving at Fremantle, Western Australia, on 13 March 1942.
Transfer to Australian service
In May 1942, the Dutch government offered K IX to the Royal Australian Navy (RAN) for use as an anti-submarine warfare training vessel. The offer was accepted, and K IX arrived in Sydney on 12 May 1942 for repairs and refitting.
At this time, Australia had become the principal Allied base in the South-West Pacific following the fall of Singapore and the Netherlands East Indies. Japanese naval operations against Australian ports, including attacks on Darwin, Broome, Exmouth and Townsville, reflected an effort to disrupt Allied supply and staging areas rather than a plan to invade Australia itself. The events that followed in Sydney Harbour need to be understood within this wider strategic context.
The Japanese attack on Sydney Harbour
On 28 May 1942, the Japanese submarine I-21 launched a reconnaissance floatplane that flew over Sydney Harbour, identifying thirteen Allied warships, including K IX. On the night of 31 May–1 June 1942, three Japanese midget submarines were deployed for an attack on the harbour.
The principal target was the heavy cruiser USS Chicago, which was berthed at Garden Island alongside the depot ship HMAS Kuttabul, with K IX moored nearby at the south-eastern corner of the island. At approximately 11.25 pm, the midget submarine M24 fired two torpedoes at USS Chicago. Both torpedoes missed the cruiser. One passed beneath K IX and HMAS Kuttabul before striking the breakwater against which Kuttabul was moored.
The explosion sank HMAS Kuttabul and killed 21 Allied naval personnel (19 Royal Australian Navy and 2 Royal Navy). The blast also destroyed storage battery jars aboard K IX, causing severe damage and rendering the submarine inoperative. K IX was subsequently towed away from the wreck of Kuttabul on 1 June 1942 and entered an extended period of dockyard repair.
In the aftermath of the raid, Allied censorship regulations instructed the press not to mention the presence or damage of K IX, in order to prevent information about Royal Netherlands Navy vessels operating within the South-West Pacific Area from reaching the Japanese. Two of the attacking midget submarines were sunk within Sydney Harbour. The third, M24, escaped and disappeared; its wreck was not located until 2007, when amateur divers discovered it on the seabed near the mouth of the Hawkesbury River north of Sydney.
HMAS K9 and training service
Following repairs, K IX was formally decommissioned from the Royal Netherlands Navy on 25 July 1942. She was transferred to the Royal Australian Navy and commissioned as HMAS K9 on 22 June 1943.
Despite her age and chronic mechanical problems, K9 played a valuable role as an anti-submarine training vessel. She was the only submarine commissioned into the RAN during the Second World War and provided Australian crews with rare hands-on experience in submarine detection and tracking at a time when such skills were urgently needed.
Her operational usefulness was limited. On 22 January 1944, a battery explosion caused significant further damage. With spare parts unavailable and the submarine already nearing the end of her service life, K9 was decommissioned on 31 March 1944, having spent only 31 days at sea during her RAN service.
Final years and legacy
After decommissioning, the submarine was returned to Dutch control and converted for use as an oil lighter. While under tow to Merauke in Dutch New Guinea, she ran aground near Seal Rocks, New South Wales, on 8 June 1945. The vessel was subsequently stripped for scrap.
In 1999, the remnants of the submarine were located by the New South Wales Government’s Heritage Office. The beach where she grounded is now known as Submarine Beach, a rare surviving place-name reminder of the Dutch submarine presence in Australian waters during the Second World War.
K IX / HMAS K9’s wartime career reflects the broader story of Dutch naval forces in exile: ageing equipment, rapid adaptation under Allied command, and a contribution that, while often overshadowed, played a meaningful role in Australia’s wartime defence and training effort.
See also : Dutch Submarines operating from Australia during WWII
