Did a well-aimed German torpedo sink the pride of the Australian navy? Or was it a catastrophic explosion in the ship's ammunition storage area that ensured that none of its 645 crew would survive?
Part of the puzzle was solved last month when a sonar search led by American shipwreck hunter David Mearns found the wrecks of battle cruiser HMAS Sydney and, nearby, Germany's converted freighter HSK Kormoran.
Both vessels sank after the Nov. 19, 1941 battle, and previous attempts to find them proved fruitless.
Until now, the official record of the battle has been based on the accounts of German survivors who were captured as they drifted toward Australia in lifeboats.
The Sydney spotted the Kormoran as it was prowling for Allied merchant ships to sink, about 500 miles north of Perth. The Australian vessel moved to intercept the suspicious ship and demanded that it identify itself. The Kormoran hedged, raising flags that claimed it was a Dutch trader and sending misleading radio signals.
All the while, the Sydney was being drawn closer until it eventually lost the advantage of having longer-range weapons.
German survivors said the Kormoran eventually dropped the artifice, raised its German ensign and opened fire when the ships were within a mile of each other.
Crews engaged in a furious exchange of naval artillery, torpedo and machine-gun fire for about half an hour, though Australia's official history says both ships were probably irreparably damaged in the first five minutes.
As they took to lifeboats and set off charges to scuttle their vessel around midnight, the Germans later described seeing the glow of fires aboard the Sydney as it drifted about 10 miles away.
For years, the Germans' account of the battle was viewed with suspicion and left important questions unanswered. Among them: If the Australian ship was able to limp away
- aflame, but afloat - why was there no sign lifeboats were launched?
The first photos transmitted from the wreck show the Sydney's turrets still trained to its port side as they were when the Kormoran was in their sights.
All the cradles where the lifeboats once hung were empty.
Naval historian David Stevens said this does not mean the crew abandoned ship. The boats were tied to the upper decks and would likely have come loose as the ship sank.
"They're the sort of stuff that gets really damaged when your upper deck is getting shot to pieces," Stevens said.
As the Germans said, the top of a gun turret was blown overboard by gunfire. One photo shows a hole blasted by a direct hit between its twin guns.
The Sydney's bridge section had clearly taken the brunt of the Kormoran's heavy gun barrage and an 80-foot section of the bow had snapped off around where the Germans recalled a torpedo struck with devastating effect.
"All you can say so far is that the Germans' descriptions are very accurate," Stevens said after seeing the initial pictures and searchers' reports.
Searchers have suspected since seeing high-resolution sonar images of the wreck last month that a torpedo weakened the hull and caused the bow to snap off, ultimately sinking the ship.
Another theory offered to explain the total loss of life is that the burning ship's ammunition storage area erupted in a catastrophic explosion.
