[CaptainofDespair]

Originally Posted by Farael

Oh, very simple... Mordor was constantly desolate, it wasn't just one season in the year, it was a barren wasteland all year round.

When we come to the War of the Ring, there are thousands and thousands of troops there. All of that is despite the desolation. And the mountains surrounding Mordor could very well harbor the orcs in their many caves. I doubt the Ephel Duath or the Ash (?) Mountains are places the Gondorians want to check.

Not to mention that the same thing happened to Napoleon, winter came around and all of a sudden his (already stretched thin) supply line just couldn't cut it.

Napoleon's supply lines were only broken after being stretched to Moscow. Had the French not gone towards Moscow, and had rather gone towards St. Petersburg, that breakage may very well not have occurred. The line to the Russian capital, while still thousands of mile long, could have held. Going to Moscow, however, leads one deep across long stetches of nothingness. Both Napoleon and Hitler made that mistake. That is an error the Witch-King would not have to contend with.

So you chose to look at the "possitive side" but you are ignoring the fact that these armies fell... within a year!! How could the WK hold such long supply lines to support his siege for twice as long?

The Wiki's supply line was nowhere near as long, and nor did he have to contend with armies nipping at his lines, as those only ran through Sauron-dominated regions. It's not hard to maintain a longer supply line if you only go through friendly territory. Combined that with the larger potential manpower over Gondor, and it becomes much, much more feasible for the Nazgul to lay siege for a longer time, and resist the relief efforts.

There is almost no explanation for whatever happens. We just get one brief line of text and a lot of guesswork.

I think Tolkien's mentioning of the fall of Ithil is quite enough explanation. The word "Siege" says it all. There is no guesswork in that, to me.

And in the light of those "unconventional" situations, what is so rare about a haunting that demoralises the troops and leads a few scared souls to open the doors to an enemy that, otherwise, would not have been enough to besiege the city without being driven off by near-by Minas Tirith/Osgiliath forces?

What is rare about it? That is the point. It is rare, to the point of being unheard of. And I do not recall a haunting being another meaning for the word 'siege'.

The simplest explanation is usually the correct one. While there are some pitfalls in explaining the fullness of either argument, the idea of a traditional "siege" fits more easily with what Tolkien wrote, and is thus the simplest explanation (in going with exactly what Tolkien wrote). A Haunting requires so much more flushing out and it does not really fit with the definition of the word that Tolkien chose. I doubt Tolkien would have come up with an entirely new meaning for "siege" without explaining it. And Tolkien obviously did not write anything to the effect of the situation of a Haunting occurring. Thus, it is far more likely that the simplest idea, that of the traditionally defined siege, is the most correct and feasible one.