War is horrible - I wonder if it hadn't been carrying mostly PoWs and it had become more well known what the repercussions would have been.
This thread has many tendrils. I'm not sure what this has to do with any of my replies as I've not said, nor implied that.
> From what I've read, the practical obligation to survivors is met once the attacker is confident that some SAR team somewhere has been notified, which was the case here.
Can you point to that in San Remo which you've referenced multiple times - or somewhere if appropriate? I cannot find sections that deal with requiring the rescue, or notification of the need for, of shipwrecked survivors in San Remo - perhaps I am not using the right terms.
Because it isn't "possible" for modern submarines to assist with rescue. They're pathetically unstable on the surface. Vulnerable as hell to even drones. Don't have a deck to speak of where rescues could be held. And have a nuclear reactor inside–you can't take randos through the airlock.
The only "circumstances permit" place where a submarine might be able to help is if it's operating in friendly waters, with air support and naval support close by to ensure no e.g. drones make a run for it while it's on the surface. And even then, it would be a risky operation.
San Remo which you referenced in another reply doesn't seem to go into what is required of combatants around rescues but it does say that rescuers can't be attacked [1]. That would make the Laconia argument be that I can't be committing a war crime by not rescuing survivors because I presume that I am at risk of having a war crime being committed against me.
[1] https://ihl-databases.icrc.org/en/ihl-treaties/san-remo-manu... : The following classes of enemy vessels are exempt from attack: ... and vessels engaged in relief actions and rescue operations;