Helm's Deep
Tolkien had not yet envisioned Helm's Deep in his first sketch for the decisive battle between Rohan and the forces of Saruman. In an outline published in "The Treason of Isengard" as “The Story Foreseen from Fangorn," the Rohirrim rode west at Gandalf's urging, as in the published text, but met the army of Saruman on the open plain. An indecisive battle ensued, after which the Rohirrim camped for the night, and woke to see the enemy surrounded and destroyed by a wood that had appeared overnight.