|Description||Earthen wall and ditch|
|Events||Battle of the Hornburg|
Helm's Dike was an earthen wall and trench that shielded the Deeping-coomb.
The ancient dike was built as an outlying defense of the Hornburg, a quarter mile in front of the burg and deeping-wall. It stretched a mile from cliff to cliff.
On 3 March T.A. 3019 King Théoden with Aragorn, Legolas, Gimli, Éomer, and other riders hurried to reach Helm's Deep before the army of Saruman could overtake them. When they came to the rampart the defenders of the dike were greatly cheered to learn of the arrival of the king, who stopped to learn of news.
In the early stages of the Battle of the Hornburg, Uruk-hai attacked the dike. Gamling commanded the defense in which many orcs were killed, but soon the dike was overrun. Though he managed to retreat the dike was broken and partially leveled.
The next morning the defenders counter-attacked the orcs and Dunlendings and drove them over the Dike. Then the king and his company stopped in amazement for a quarter mile beyond the Dike was a new, nameless wood. In the space between the host of Saruman was caught in panic until, with the arrival of Gandalf and Erkenbrand, the orcs fled into the forest.
As the victors rested, those who had been driven back into the caves (Gamling, Éomer, and Gimli among them) came over the wall to greet their friends. Later, near sunset, Théoden, Gandalf, and the others left the Dike on their way to Isengard.