Sauron's hurry for War?

[MLD-Grounds-Keeper-Willie]

Wasn't it suggested in the books that Sauron might have thought the ring would be taken to Gondor? I think that's why Sauron was breeding war on Minas Tirith. And then, when Pippin looked into the palantir, didn't Sauron truly believe that the ring was with the hobbits in Isengard? Sauron sent a nazgul speeding to orthanc faster than you can say Mordor. I think that Sauron was trying to destroy minas Tirith before the ring could reach it.

Doug, you said

either Aragorn or some other great leader is going to use it to challenge his power

I don't think that Sauron thought that. Sauron did not think that Aragorn was going to use the ring or that someone else would. Aragorn was simply challenging Sauron's mind when looking in the Palantir. Aragorn won and Sauron knew then that Aragorn lives! Sauron was deeply troubled to know that the hier of Isildur exists and Sauron does not forget the blade of Elendil.

So that's another reason why Sauron pressed war. Perhaps he wanted to destroy Minas Tirith or gain the upper hand before teh king of Gondor claims the throne, because that would not only add a great warrior, but it would lift the spirits of the soldiers/people and give great courage and pride. Well, you get the picture.