During the early part of her operational history, Sydney helped enforce sanctions during the Abyssinian Crisis, and at the start of World War II was assigned to convoy escort and patrol duties in Australian waters. In May 1940, Sydney joined the British Mediterranean Fleet for an eight-month deployment, during which she sank two Italian warships, participated in multiple shore bombardments, and provided support to the Malta Convoys, while receiving minimal damage and no casualties. On her return to Australia in February 1941, Sydney resumed convoy escort and patrol duties in home waters.
On 19 November 1941, Sydney was involved in a mutually destructive engagement with the German auxiliary cruiser Kormoran, and was lost with all hands (645 aboard). The wrecks of both ships were lost until 2008; Sydney was found on 17 March, five days after her adversary. Sydney‘s defeat is commonly attributed to the proximity of the two ships during the engagement, and Kormoran‘s advantages of surprise and rapid, accurate fire. However, the cruiser’s loss with all hands compared to the survival of most of the Germans has resulted in conspiracy theories alleging that the German commander used illegal ruses to lure Sydney into range, that a Japanese submarine was involved, and that the true events of the battle are concealed behind a wide-ranging cover-up, despite the lack of evidence for these allegations.
 | HMAS Sydney |
| Page 1 |
 |
| HMAS Sydney seen in 1936. |
 |
| HMAS Sydney seen in 1938. |
 |
| HMAS Sydney seen passing under the Harbour Bridge, Sydney, NSW, Australia, date unknown. |
| (Photo from the collection of W/O Henry T. G. Hunt, R.A.A.F.) Courtesy of Sandy and Les Cridland |
 |
| HMAS Sydney seen in Sydney Harbour, date unknown. |
| (Photo from the collection of W/O Henry T. G. Hunt, R.A.A.F.) Courtesy of Sandy and Les Cridland |
 |
| HMAS Sydney, date and location unknown. |
 |
| HMAS Sydney, date and location unknown. |
 |
| HMAS Sydney, date and location unknown. |