Description
The Black Gate blocked the pass of Cirith Gorgor, the gap between the Ephel Dúath and the Ered Lithui in the northwestern corner of Mordor. The Black Gate was a single gate of iron, which consisted of two vast iron doors under a frowning arch, in a rampart of stone with a battlement that stretched between the high cliffs on either side of the mouth of the pass. On two sheer, black-boned and bare hills that were thrust forward from the mouth of the pass stood two strong and tall towers, the Towers of the Teeth.
Immediately north of the Black Gate was the Desolation of the Morannon and the Slag-hills. Further north of it was the Dagorlad. North of the Black Gate a road running north from Ithilien met another road that went north in the direction of the Dagorlad and a third road that ran east along the Ered Lithui. South of the Black Gate was the valley of Udûn that led to the plain of Gorgoroth in Mordor.
The Black Gate was built by Sauron after he chose Mordor as a land to make into a stronghold in S.A. 1000.
In S.A. 3434 the Battle of Dagorlad took place at the plain Dagorlad in front of the Black Gate.
After Sauron's fall, the Men of Gondor built the Towers of the Teeth to prevent his return to Mordor and the Black Gate was manned by the forces of Gondor.
After the Great Plague devastated Gondor in T.A. 1636, the watch on the borders of Mordor ceased and the fortresses that guarded the passes were unmanned in T.A. 1640 because of a lack of troops. It is possible that the Towers of the Teeth and the other fortresses that guarded the passes into Mordor were only abandoned temporarily and were manned again by troops from Gondor when sufficient troops became available again later.
In T.A. 1944 when king Ondoher of Gondor and both his sons fell in a battle against the Wainriders north of the Morannon the Morannon and the Towers of the Teeth were still manned by troops from Gondor.
As the strength of Gondor failed the Towers of the Teeth and probably also the Black Gate were abandoned by the Men of Gondor and stood empty for long years. It is possible that the Black Gate was occupied by the forces of Sauron after the Witch-king came to Mordor in T.A. 1980.
During the War of the Ring, on 24 March T.A. 3019, the Army of the West, numbering under 6,000 men, arrived at the Black Gate with the intention of drawing the Eye of Sauron away from Mount Doom, to allow Frodo the Ringbearer to cast the One Ring into the Crack of Doom within it. On 25 March, T.A. 3019 the Army of the West challenged Sauron. As a reaction, the forces of Sauron came out of the Black Gate, an army of Easterlings that had hidden in the shadows of the Ered Lithui beyond the eastern Tower of the Teeth approached and orcs poured down from the hills on either side of the Black Gate and attacked the Army of the West. When the One Ring fell into the Cracks of Doom the volcano Mount Doom erupted, and the Towers of the Teeth, the rampart and the Black Gate collapsed in an earthquake. The forces of Sauron fled, most of the Men of Rhûn and Harad fled eastward, some of them surrendered and the rest were destroyed.