[Farael]

Well, I was going to post something rather similar to what Kuruharan has said about the supply lines... sending food and equipment over hundreds of miles of (at best) deserted, if not full of bandits, terrain is no easy task (and no, the fact that the Nazghul are "baddies" does not mean that they won't be attacked by bandits. There are quite a few instances of orcs attacking other orcs and ultimately benefitting the "Good" people, not the less the massacre of the tower of Cirith Ungol which allowed Sam and Frodo to escape).

But there is another side to this matter. Reinforcements. I believe we have all agreed that the Nazghul did not have a huge army. Furthermore, if they could not gather a huge army, how could they find reinforcements? As Kuruharan mentioned, Gondor could easily besiege the Nazghul fortifications and bide their time. Two years is a lot of time, and yet not enough time for the Nazghul to build a fortress out of thin air. Best case scenario, they'd have a wooden pallisade with a big ditch and stakes to prevent a cavalry attack. All nice and dandy, but I'm sure Gondor could get a catapult or two. Just keep on shelling them, they can't replace their losses. Furthermore, as I mentioned, their fortifications are not likely to have been made of stone... thus easily breakable by a good solid chunk of rock flung by a catapult. And don't ask me where they'd get rocks from, they are near a mountain range!!!

Furthermore, it seems we are forgetting one little thing. There are still some forces in Minas Ithil, so the Nazghul would have been fighting a battle in two fronts. At any point in time, and with the help of the Palantir which made comunications easy, the Gondor forces could attack the Nazghul on two fronts... the main force would start an attack, and at the heaviest point a smaller force from Minas Ithil could attack the enemy at their rear. Say, give the Nazghul a month to get their fortifications in place, shell them for a day or two and then attack them in two fronts. A determined attack on two fronts would dislodge any army... the catapults would negate the "fortifications" (or some of them anyway) and furthermore, they'd cause at least some losses that the Nazghul could not replace.