What was fascinating to me was that the first US commercial ship sunk by Germany was sunk on the south side of Australia! I found that by accident clicking around. Truly a world war, I suppose.
The reality is that the heavily armed "merchant ship" Kormoran was a stealth convert by the German Navy and generally referred to as the German auxiliary cruiser Kormoran.
The Kormoran was approached by the RAN warship HMAS Sydney for signaling and inspection, figuring that its game was up it unloaded everything it had fatally damaging the Sydney and taking on terminal shelling in the process.