Battle of Igon's Cliffs

The Battle of Igon's Cliffs is most commonly misinterpreted by those uneducated enough to do so to be the point of extinction of the Orc race. It, in fact, served as a warning for the Orcs, to wait for another war to break out and attack then, when their enemies were at their weakest, whereupon Orc domination over the realm would be absolute.

History
After Narod Glarmog led his legions on the fateful siege of Khiburheim, he was shot by an arrow launched from one of his own archers. The Orcs subsequently fell into disarray, and, led by Oqugan Naxtreg, fled west, to Igon's Cliffs, a location where they hoped to stand ground against the Dwarven retaliation.

Igon's Cliffs are actually a number of very small peninsulae. Most texts do not cite them as being such, instead choosing to list Igon's Cliffs as a singular location.

The cliff that the Orcs fled to, Argardar's Tooth, was of a favorable position for the Orcs - it provided a significant elevation advantage, a wet grassland where Dwarven mail-boots were not made to traverse, and a very suitable firing position for their archers.

However, the Orc race functions based on a swarm mentality - a leader is responsible for the army's movements, positions, and distribution. Without a suitable leader - Narod Glarmog - the legion could not fight effectively, yet they managed to hold their ground for an entire day. On the dawn of the second day, the sun rose, blinding the Orc army and giving the Dwarven assaulters a chance to retaliate. They charged, and with a collective effort pushed the Orc army over the cliff and into the sea.