View attachment 240370
What is this tom-foolery??!!
Capturing a capital ship is extremely rare, you're lucky to have witnessed it first hand, I have never, since HoI2 was released, seen it first hand.
Here's from another thread, posted by a dev:
"There's a (quite) slim chance to capture enemy fleets in port.
It is based on a random factor (0..99) + FleetSize*5. The fleet will be captured when the result is under 10 AND there are no loaded with troops transport ships in the fleet.
As you can see only fleets of 1 ship (this gives 5 points) can be captured with a 5% chance (0 to 4 random factor out of 100)."