Thirsk was interrupted in is narration just before he was shot, but from the context I expected him to finish the sentence saying something like "we currently have no way to duplicate the heretic's armor on our own ships." That's gotta be a sobering thought for the CoGA.
Yes, they'll learn how to duplicate the gun's carriages, but they really can't duplicate the ammo very efficiently. Every shell would have to be hand-made.
We're really making too much of a fuss about this, since the KHs will arrive in the Gulf of Dohlar by next spring, and as Howsmyn mused as he looked at them under construction, a single one of them could destroy every ship in existence. The only effective navy other than the ICN is the RDN, which just took huge losses against a single ironclad that to be truthful, was merely a prototype to prove the concept of armoring ships against shells, and the Thunderer doesn't pack the newest guns or the smokeless powder rounds that will soon be available.
So should the RDN make its repairs, add the Thunderer to its fleet, and sail bravely off to drive the pesky Charisians off of Claw Island and out of the Gulf, they're going to find out rather abruptly that their exciting new toy can be destroyed by a few shots from its sister ships and especially by its big brother - a big brother that doesn't care if the wind is blowing in the direction it wants to go, or even if there's any wind at all! Plus I expect a few city ironclads will arrive as well, and RFC is on the record saying any one of them could destroy the entire RDN, and presumably all the coastal fortifications in existence. The screw galley's 150 lb. shells wouldn't do much to a city ironclad either - or the Haarahld's, whose shells could shatter them from miles away.
So the "defeat" of the ICN in HFQ was merely the loss of a bunch of obsolete ships, including the ironclads. It was the loss of the sailors that hurt the most, and I'm really glad that we didn't have a repeat of the POWs undergoing a ghastly trip to Zion via land to be tortured to death.
Kudos for bringing Yairley into the inner circle, and I very much enjoyed the battle and the rescue, since I wasn't holding out much hope that they'd get the POWs back alive. His struggle with the Big Reveal while clinging to his duty showed that accepting the truth isn't always going to be easy even for those who have rubbed shoulders with members of the inner circle, especially for those whose belief defines who they are, like DE. (So they won't even try with him, he'll just get lots of visits from seijins.)
While I've posted my expectations that Nimue/Merlin would rescue Thirsk's family for years, I was surprised that the CoGA grabbed them this soon and sent them by ship. That said, the battle with two shotgun-wielding seijins was enjoyable, although using the skimmer to drop a 500 lb. bomb and fire machine guns was overkill when blowing up the CoGA ship to leave no witnesses. A SNARC blowing up in the ship's magazine would have done the job without running the chance that anyone would see the skimmer from afar. So I'm guessing that using the skimmer during rescue was to tip us off that Merlin is thinking of how to use it given the limitations imposed by the OBS, and to show us that it has those capabilities to use in the future...

Having the disappearance of Thirsk's family blamed on the CoGA was a clever twist that I didn't anticipate, since it solved the problem of keeping Thirsk in command after his family disappeared. I expect that his conversation with Merlin will cover two basic points: his family is safe in Charisian hands, and to preserve the lives of his sailors, he needs to prepare his captains to strike their colors quickly should they encounter something they can't hope to defeat. I highly doubt that Merlin will ask him to defect, and since the RDN is doomed by next summer, Merlin would vastly prefer to avoid a massive bloodbath.
Thirsk will wonder if he's being blackmailed of course, but that's not Cayleb and Sharley's style and Dohlar is heading in the direction of becoming a failed state. Getting them out of the war, like Desnair has done, would go a long ways to gutting the Jihad. Thirsk can be influential in bringing that about, and in taking part in the government that results after Dohlar declares neutrality or sues for terms. King Ronnie will abdicate, so expect a regency. We all think Thirsk and Ahlverez may serve on it, although RFC will probably throw another curveball at us. Clyntahn could summon Thirsk to Zion for the audacity of encouraging the RDN to surrender without being totally blown to smithereens and dying for a doomed cause. (Although I doubt the RDN would allow the Inquisition to enforce any such order.)
So in retrospect, I fell into the same mindset as many who have posted in this thread that the loss of the two ironclads seemed a bit contrived - but I felt that way mostly because I overestimated their importance. Their replacements are en route, and a few KHs will soon follow. The "loss" in which the Thunderer gutted the western fleet of the RDN and was captured isn't going to matter in the long run - or in a few months!
