This is correct.
Yes, but it would have been easy to signal the ship to surrender, and as @robby pointed out ten posts ago, they could have convincingly made the argument that not surrendering at once would mean a Mark 48 (which they would surely know what it is, them being Navy men) was on their way. The sub, even announcing that it was in the vicinity, was safe from that toy frigate (see gnotaill’s description of it one post after robby’s). A Mark 48 is unstoppable and unavoidable. That is what I mean by not necessary. At all.
But manly crews prefer a sinking to taking prisoners and capturing a ship with all the intellingence they could have gathered from it. It’s even better than pull ups. It was a push over. So easy, I hope they enjoyed it and they get a medal and a promotion. /s
So yes, indeed, as What_Exit writes, it is correct that they were fair game. Still superfluous, mean, unnecessary, and a waste of life, material (a Mark 48 is not cheap, after all) and good will from neutral observers.
Did I make clear that I think it was stupid? So in caracter.
Fuck. Them.
The more I think about this, the more it bothers me. And yes, I do recognize the sarcasm, however a couple observations:
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I strongly suspect that the torpedo firing was not the submarine captain’s idea, and likely came from tasking orders. There are several facts which support this: 1) IRIS Dena was well armed against airborne threats, primarily surface to air missiles. 2) actually firing an ADCAP at an adversary makes the submarine vulnerable to detection. 3) despite the fact that the “toy” was not much of a threat to the submarine, the Indian ocean is very big and adversaries are many. It is probable that the submarine’s presence was made known to adversaries other than Iran when the torpedo was fired. 4) The US Navy does not deploy submarines to an operating area because of the presence of an Iranian frigate, so it is highly likely that the submarine was there for a different mission entirely.
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From that, I surmise that the SSN launched attack was deemed to be the least risky by command. Sending aircraft to strike a platform armed with SA missiles can be costly and potentially fail. Striking a surface ship with an ADCAP (Mk 48 torpedo) is low risk/high chance of success.
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Submarines just don’t fire from the hip at targets of opportunity, and I highly doubt that this was a chance encounter. The submarine was very likely tracking and following IRIS Dena for several days before the attack, and only did so when it was determined that no safer option was available. Nevertheless, it is highly unlikely that they were sent to the IO just to take out a 1500 ton frigate in transit. There is a very good reason that we don’t yet know which submarine executed the attack - it is probably still in area and now carrying out its original mission. It will likely be more than 6 months before we find out which boat it was.
While I strongly agree that this attack was largely unnecessary and of little tactical or strategic value, characterizing this as a display of “manliness” is disingenuous and short sighted. I am also very concerned about the circumstances that put IRIS Dena in this operating area (Indian naval exercise MILAN) and the diplomatic implications with India - especially now that Pakistan is openly at war with Afghanistan.
This isn’t a crew that I expected. I don’t have military experience and am not familiar with crews on ships.
There are a lot of officers on that ship.
Maybe they were passengers that participated in the naval exercise?
Anyway, their involvement in this war is over.
btw, the crew breakdown totals 203, not 180. 
Link Sri Lanka takes control of second Iranian vessel a day after US sinks warship
That is a really weird rank breakdown for the company of a military ship. I don’t know naval customs and politics in the Revolutionary Guard, but that’s way beyond even what I would have expected of navies which use junior officers like the US Navy uses ratings and warrant officers.
The only thing that occurs to me is that the cadets may be on a seamanship training cruise, so working as the equivalent of the able sailors. Putting them over on the “sailors” side feels like it balances out better.
Obligatory Disclaimer: I was a career wing-wiper so everything I know about shipboard staffing practices is 2nd hand or worse.
Agreed. Submarine captains don’t decide on their own to engage and sink a ship unprovoked when we are [checks notes] not at war.
There were 42 ships for 17 different nations. Emphasis was on anti-submarine efforts and Electronic Warfare. I strongly suspect the US sub was monitoring the exercise for intelligence purposes. When the Iranian ship split, the sub followed. Higher-ups determined the ship was a threat to US assets (anti-ship missiles) and gave the order.
We don’t know what orders they were given; with Trump and company it may well have been a simple “kill anything that moves, that’s what Tough Guys do.” And Hegseth did boast about how we were no longer operating under “restrictive, minimalist rules of engagement”.
I think during World War I, the German U-Boats would warn merchant ships and give the crew a chance to abandon ship before sinking it. But then the British starting arming merchant ships, and, after a few U-Boats were sunk, the Germans just torpedoed a ship without surfacing first.
A ship that survived Pearl Harbor, sunk by a 1920’s designed torpedo, fired from a nuclear powered submarine. That war was all about creating questions for trivia buffs!
I wonder if some of the officers were actually passengers and not the “crew” of the ship. Since they were returning from a naval conference, they may have just been attending the naval conference and took a ship home rather than a plane.
The media is notoriously bad at discerning between naval officers and enlisted. Any time an enlisted sailor with a rank of E-4 or above (i.e. Petty Officer) is mentioned in a news article, 80% of the time they are called “naval officers” by a reporter. Complicating that, foreign navies sometimes have different rank structures. I have no familiarity with the Iranian navy, but anytime someone in the media talks about officers and enlisted it should be taken with a grain of salt.
They did break enlisted into enlisted and senior enlisted, so maybe not this time.
I get 208, but yes, and the normal complement for that class of frigate is 150. It’s probably safe to assume that the ship was loaded with “cadet officers” (what we would call midshipmen) who were participating in the exercise but not part of the crew.