Theoden did say that, after Saruman proposed peace with Rohan. Consult-
The Lord of the Rings: The Two Towers
Chapter X: The Voice of Saruman; page 566, line 22. Here's exactly what the book reads:
"We will have peace," said Theoden at last thickly and with an effort. Several of the Riders cried out gladly. Theoden held up his hand. "Yes, we will have peace," he said, now in a clear voice, "we will have peace, when you and all your works have perished - and the works of your dark master to whom you would deliver us. You are a liar, Saruman, and a corrupter of men's hearts. You hold out your hand to me, and I perceive only a finger of the claw of Mordor. Cruel and cold! Even if your war on me was just - as it was not, for were you ten times as wise you would have no right to rule me and mine for your own profit as you desired - even so, what will you say of your torches in Westfold and the children that lie dead there? And they hewed Hama's body before the gates of the Hornburg, after he was dead. When you hang from a gibbet at your window for the sport of your own crows, I will have peace with you and Orthanc. So much for the House of Eorl. A lesser son of great sires am I, but I do not need to lick your fingers. Turn elsewhither. But I fear your voice has lost its charm." (paragraph) The Riders gazed up at Theoden like men startled out of a dream....
That's exactly what the book says, word for word. If you are somehow related with the production of the Lord of the Rings books or Tolkien, please do not sue me, as I am only doing this in an answer to a question.
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Here is one thing that the Fungi Forums can be sure about. If the day of war against TUNMB ever strikes, you may rest assured that the SMFCMB (Super Mario Fan Club Message Boards) are with you. As for the thing about the war not hurting anybody...hmmm.... En Garde! *unsheathes sword*
Just kidding. *sheathes sword* I hope the line above will not start Forum War I.
LieutenantEagle
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Gandalf: The Eagles have come! The Eagles have come!
LieutenantEagle: I know. They''re in front of you.