Its purpose was to guard the Causeway against any enemy attack.
During the War of the Ring, they were guarded by Faramir and the men under his command. At the start of the Battle of the Pelennor Fields on March 13, 3019, the Causeway Forts were overrun and captured by the armies of Mordor under the Lord of the Nazgûl, and Faramir and his troops were forced to retreat.
- The Lord of the Rings pgs. 750, 807, 817-18
- The Complete Guide to Middle-earth
- The Atlas of Middle-earth pg. 153