'navy ship' - commissioned in a state's navy, not a submarine

'sunk' - could sink immediately, could sink on the way back to port, could be scuttled

'ship-to-ship combat' - whatever the method of attack, it needs to originate from another opposing vessel. It could be a missile, a torpedo, a shell. If it is a weapon launched by an aircraft that took off from a ship this counts.

If there is doubt or a lack of clairity as to what exactly happened, I will make a good faith attempt to correctly resolve to the most likely (Occam's razor) to be true version of events

(more than 2,000 tonnes is designed to select for corvettes and larger, ie 'warships' as opposed to smaller attack craft, but it also captures a range of support vessels, as well as amphibious assault ships and aircraft carriers)