[Gordis]

Originally Posted by Legate of Amon Lanc

"He knew much of the mind of Sauron"
Not that Sauron is one who takes advice from anyone, but this one had probably the closest to it.

He spoke for the Lord - therefore, not to err in rendering Sauron's words, he had to understand his intentions - get some additional explanations. But a spokeseman for Sauron is not the same as his Prime Minister, and far less than his second-in-command.
and see here :

if there was any in the world in whom [Sauron] trusted it was the Lord of Angmar - RC p.262

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"The Lieutenant of the Tower of Barad-dûr he was"
Indeed, but not the "Lieutenant of Sauron", not his Second in command. The Morgul lord was Sauron's second in command, his most trusted servant, not MOS.

there was even debate here back then whether he couldn't have been of higher rank than WK himself (nonsense in my opinion, however not that overstretched).

Nonsence, indeed, AND quite overstretched IMO.

As I said, the leutenant was not a clear-cut rank. The lieutenant of Minas Morgul Tower is not the same as the Lieutenant of the Morgul Lord - who happens also be the overall head of the army of Mordor and allied forces.

In Minas Morgul, there could have been a man -XXX - the lieutenant of the Tower of Morgul - similar to MOS with similar functions, also, likely, not a warrior but an administrator. But his functions wouldn't entail replacing the Commander of Mordor army when he was slain, anymore than MOS would replace Sauron in case something happened to him. The WK would.

Sauron put the Morgul Lord in command of the Army. Would XXX, his lieutenant of the Minas Morgul tower automatically become second in command of the army? - no way. The Second in command would be appointed separately - and he would be a warrior of high rank, almost certainly another nazgul. Not Khamul, as this one was most probably in the North, but Gothmog.

It was not a sort of custom that can be broken wilfully, no, indeed, only the "low master of treachery" would do that.

And Sauron was one himself and judged the others by his own standards - for instance, he couldn't understand how the other side would reject the Power of the Ring. That's why he lost, ultimately.

Yes, but the root of my idea is that the Nazgul were not there as part of the army. They had nothing to do with the attack on Minas Tirith. They were there as "outside force", to mess around and eventually carry messages and scare Faramirs.

I wouldn't say they had nothing to do with the attack on MT. They were shrieking overhead for several days, but given their mobility, it wouldn't prevent them from being in command of parts of the army. Some were, I think, while the others carried orders and circled over the city. Maybe they took turns to let the Beasts rest. The WK was alone at the Gate and when he came for Theoden, but most likely it was because the others were quite busy elsewhere or maybe the WK sent them away to get all the glory.