Gondorian Military Forces
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In The War of the Last Alliance
Within a century of Gondor's founding, it was put to a severe test during the War of the Last Alliance. In alliance with Arnor and Elven forces from Lindon and Rhovanion, Gondor fought a series of battle against the forces of Sauron. Sauron's ground forces were completely infantry based, and the allies were predominately infantry as well. This was a result of having brought few horses with them after the Downfall of Númenor. The War was a long struggle of attrition involving hundreds of thousands of troops on each side, and Gondor's casualties were serious while Arnor's were crippling. In this great conflict, Gondor's troops fought in close, well ordered regiments, with infantry in front and archers behind. Archers were also used as mobile reserves, with companies of them moved from on weak spot in the battle line to another.
Gondor's infantrymen were well-armoured, carrying large, broad shields. They were made of multi-layered wood, and edged in metal. They always bore the device of the tree of Gondor, in metal. Infantrymen wore heavy armour, so they definitely considered heavy infantry. Above their tunics, they wore a layer of chain mail extending down to their knees and elbows. This ended with heavy gauntlets on the forearms, and heavy knee boots. Soldiers also wore plate armour, with a heavy embossed breastplate and backplate. Steel greaves extended downwards from the breastplate to the knees for added protection. All of this was topped off with a large steel helmet, with cheek plates, and a curved neck piece to protect the next from enemy blows. Decorative wings were usually attached, and the helmet was often edged in bronze. 
The weapons used by the infantry included spears, swords, axes, and bows. Gondorian spears were very long, about nine feet in length. The point was made of steel, and often two feet long. It was designed to be used as a thrusting weapons, as opposed to elven spears, which were often thrown. Swords were usually of medium length — longer than a short sword, but shorter than a broadsword. They were heavy blades usually pointed and designed to be used one-handed, either thrusting or chopping at an opponent. While the pommel was polished wood, the sword guard was usually made of bronze. In close hand-to-hand action, axes would sometimes be used. These were usually single-edged, and about three feet in length.
The Third Age
During the Third Age,Gondor's military prowess eventually weakened. The soldiers used two different types of armour and shields. The first one was the same as the ones used in the War of the Last Alliance and were still being used when Gondor was ruled by the Kings,however when Gondor was ruled by the Stewards instead of Kings (this was during the second half of the Third Age), this caused their armour and shields to change.The shields that they carried changed and was only about half the height of it's user which was made of metal. Their armour was affected as well, for it was made out of a thin layer strip of metal that would block against a few attacks, unlike the one used in the Second Age which could block many attacks. The weapons were the same (ex. spear, sword, bow and arrows) throughout the Third Age. Another major difference was their soldiers: although the soldiers would have proudly fought to the last man, they were never as strong as the warriors of the past especially by the second half of the Third Age. After the Great Plague and the Kin-strife, which left Gondor very weakened, the Gondorian troops mostly consisted of regular soldiers for the rest of the Third Age. Many Númenóreans of pure blood had perished during those troublesome times.
Cavalry of Gondor
Traditionally, Gondor had a small cavalry force. In the last quarter of the Third Age, it's close ally Rohan often supplied its main cavalry component. This was true during the Wainrider/Balchoth War, and well as during the War of the Ring. Before the Battle of Pelennor Fields, a mixed force of infantry and cavalry retreated from the Causeway Forts and Osgiliath to the citadel of Minas Tirith. Pursued by Orcs on the ground, and Nazgûl from the sky, these forces were in great peril. Lord Denethor, Steward of Gondor, finally released a mounted counter-attack against them, which drove them back. Leading this attack was the Prince Imrahil of Dol Amroth, and his mounted swan-knights. These men represented the elite cavalry force of Gondor.
Gondor. They were often in action against opposition naval forces from Pelargir or Umbar, renegade fiefs of Gondor.
Before the Downfall of Númenor, it had been known as a mighty sea power, the greatest that ever existed in Middle Earth. Previously they had sent great fleets, under Minastir, to the aid of Gil-galad against Sauron in the middle of the Third Age. Elendil and his sons, who founded Arnor and Gondor, were all great mariners; therefore, there was a long distinguished tradition of shipbuilding, sea exploration, and sea-power projection. By T.A. 830, Falastur was engaged in heavy fleet building, and became know as the first of the Ship-kings of Gondor. These fleets were usually based at Pelargir, and sometimes Umbar. After the Kin-strife in Gondor, the defeated rebels took refuge in Umbar, where they long troubled Gondor. Late in the Third Age, Thorongil (Aragorn II) led a Gondorian naval task force in a raid known as the Surprise Attack on Umbar. This was a successful raid that neutralized the Corsairs' naval power for decades, and reduced the southern pressure on Gondor at a time when its power was waning.
Gondorian Special Forces
Several groups were armed men operating often behind enemy lines. Late in the Third Age, and the power of Mordor grew, Gondor withdrew most of its conventional forces from east of the Anduin, including North and South Ithilien. They did not abandon the area completely, however, and maintained a guerilla presence there, the Rangers of Ithilien. During the War of the Ring, this force was commanded by Faramir, son of Denethor II. They acted as a reconnaissance force, and often harassed Sauron's forces.
- ↑ Chris Smith, The Lord of the Rings: Weapons and Warfare, "The Last Alliance of Elves and Men", pp. 5-6
- ↑ 2.0 2.1 Chris Smith, The Lord of the Rings: Weapons and Warfare, "Númenóreans", pp. 25-27
- ↑ J.R.R. Tolkien, The Lord of the Rings, The Return of the King, The Siege of Gondor
- ↑ J.R.R. Tolkien, The Lord of the Rings, Appendix A