Sydney sailed from Fremantle on Armistice Day, 11 November, 1941 to escort the troopship Zealandia to Sunda Strait where she was to be relieved by the British cruiser HMS Durban for the last leg of the voyage to Singapore.
The voyage was without incident and at noon on the 17 November, Zealandia was turned over to Durban and Sydney then proceeded back to Fremantle where she was expected to arrive on the afternoon of 20 November 1941.
She did not arrive as expected and the District Naval Officer, Western Australia , reported accordingly to the Naval Board at 11 a.m. the following day that Sydney was overdue. This did not immediately concern the Naval Board as they had been advised that Zealandia had arrived later than anticipated and it was assumed that Sydney too had been delayed.
There was also the possibility that she might have been diverted for another purpose and had not broken radio silence. When however, she had not returned by 23 November, she was instructed by the Naval Board to report by signal. There was no reply
Returning from her convoy duties to Java, Sydney was proceeding south along the north west coast of Western Australia when she sighted what appeared to be a merchant vessel at about 1600 on 19 November 1941, some 130 miles west of Shark Bay.
The ship was in fact the German raider Kormoran, (Commander Theodor Detmers) disguised as the Dutch merchantman Straat Malakka . Sydney challenged the vessel continuously using her searchlight whilst at the same time closing the range between the two ships.
Sydney‘s efforts to establish the true identity of the vessel resulted in her closing the range to a point where she no longer had the advantage of her superior armament. At approximately 1715 Sydney had drawn almost abeam of Koromoran to starboard, less than a mile distant. Both ships were steering West-South-West at about 15 knots. The Australian cruiser was at action stations with all guns and torpedo tubes bearing. Her aircraft was on the catapult with its engine running. She then signalled, both by flags and flashing light; ‘Where bound?’ Kormoran replied ‘ Batavia ‘. The crucial moment then came when Sydney hoisted a two flag signal consisting of the letters ‘IK’ which the raider could not interpret. They were in fact the two centre letters of the Straat Malakka‘s four letter secret identification signal. With no reply forthcoming Sydney signalled in plain language ‘Show your secret sign’.
Finally, when concealment of his vessel’s true identity was no longer possible, and with the advantage of surprise, Detmers ordered the Dutch colours to be struck, hoisted the German Naval Ensign and opened fire at approximately 1730 with all armament at a range ‘somewhat more than a mile’.
It is likely that the raider’s first salvo destroyed Sydney‘s bridge, with the result that her primary control was immediately put out of action. Sydney‘s own guns opened fire almost simultaneously with a full salvo that passed over Kormoran without inflicting damage. Kormoran again scored hits on Sydney with two salvos again hitting her bridge and midships section. According to the Germans all of Kormoran‘s armament was brought to bear on Sydney, concentrating on her bridge, torpedo tubes and anti aircraft batteries.
With her stem low in the water, Sydney now turned sharply towards Kormoran as though attempting to ram. As she did so, the top of “B” turret was blown off and flew overboard, the cruiser then passed under Kormoran‘s stern, heading to the southward and losing way. Kormoran , maintaining her course and speed, was now on fire in the engine room where hits by Sydney‘s “X” turret had caused severe damage. Smoke from the fire hid Sydney from Kormoran‘s bridge but the raider continued to engage with her after guns as the range opened to approximately 4,400 yards.
At about 1745. Sydney fired four torpedoes. Detmers was then turning to port to bring his broadside to bear, however as he did so Kormoran‘s engines began to fail. The torpedo tracks were sighted, but Kormoran cleared them and they passed astern. Simultaneously the raider’s engines broke down completely.
Sydney , crippled and on fire from the bridge to the after funnel, steamed slowly to the south returning only sporadic fire from her secondary armament. Although by now the range had opened to 6,600 yards Sydney continued to receive steady hits from Kormoran‘s port broadside. At 1800, at a range of 7,700 yards, Kormoran then fired one torpedo that missed Sydney‘s stern. Although this fierce action had lasted only half an hour both ships had been dealt mortal blows.
Kormoran fired her last shot at 1825 at a range of about 11,000 yards. In all, she fired approximately 450 rounds from her main armament and hundreds from her anti-aircraft batteries. With the gathering gloom the form of Sydney disappeared from view and was last seen by the Germans about ten miles off, heading approximately South-South-East. Thereafter, until about 2200, all that was seen was a distant glare then occasional flickerings until midnight at, which time all trace of, Sydney disappeared.
Of Sydney‘s total complement of 42 officers and 603 ratings, none survived. The only material evidence recovered from Sydney was an Australian naval type Carley life-float recovered eight days after the action by HMAS Heros and an Australian naval pattern life-belt recovered by HMAS Wyrallah . The Carley float is now preserved in the Australian War Memorial in Canberra