The Battle of Helms Deep:

One of the major battles in the War of the Ring, the Battle of the Hornburg occurred on March 3rd 3019. This was a battle between Rohan and the armies of Saruman, then known as Saruman the White. The forces of Rohan had the aid of the Huorns from Fangorn Forest and were victorious.
Saruman's armies contained Orcs, Wolf-Riders, Half-orcs and Dundlendings. They also had a "blasting fire" with which they took the Wall of Helms Deep. They did not take the Hornburg and were defeated by both Rohirrim armies and the Huorns, so soundly that few orcs returned to their master.
It was during this battle that Gimli discovered the Glittering Caves of Aglarond where he later settled with many other dwarves.