As a follow up to this question: What did the nine actually achieve for their master during the war of the ring?
The only major thing I can think of is that they killed Theoden. was there anything else?
As a follow up to this question: What did the nine actually achieve for their master during the war of the ring?
The only major thing I can think of is that they killed Theoden. was there anything else?
Let's look at everything they did and tried to do, book by book:
In the Fellowship of the Ring, it is unknown who tortured Gollumn and obtained information about the Ring. Speculation is that Sauron did it, although it is likely that one or multiple Nazgul helped. They were sent to search for the Ring in the Shire, and came very close to getting it several times. The Witch-King did stab Frodo with a Morgul blade, which should have turned Frodo into a wraith that would have turned the Ring over. During the Fellowship's journey, they were used as scouts on their flying steeds, as seen when Legolas shoots one down.
The Nazgul make limited appearance in the Two Towers, although they are apparently used as scouts and messengers. IIRC, a Nazgul was once dispatched to Isengard for some reason by Sauron, but it's been awhile since I read the books, so I don't remember what that purpose was. Of course, by the Return of the King, they were put to the use Offensively in the assault on Osgiliath and Minas Tirith, as well as the Black Gate. The Witch-King was the effective commander of the armies of Mordor, and we assume at least some of the strategy was his. They were effective at terrifying their enemies and motivating their forces, so it's safe to say they were pretty effective here. Additionally, they were used as one of Sauron's last defense in the Battle of the Black Gate, and they were sent to Mount Doom once Frodo claimed the Ring.
It seems the Nazgul were used mainly as scouts during the War of the Ring, and they probably were effective at detecting anything larger than the Fellowship. They were great military leaders in the past, although by the time of the War of the Ring Sauron relied on pure military might rather than the skills of the Nazgul. On the surface, they did not seem effective although as noted in the question you linked, they simply ran into numerous unforeseen obstacles. It is likely they performed more duties behind the scenes.