Armor

Armor was metal plating or leather pieces designed to provide protection to the wearer and was available for purchase at blacksmiths. They fortified the health and damage resistance of the wearer. However, armor could also be broken if it took too much damage causing a temporary loss in maximum health until repaired.

High Middle Ages
During the Crusades, Altaïr wore a standard Assassin combat uniform that primarily consisted of vambraces, greaves, shoes and a protective belt, all made in leather. The main vambrace, which was always worn on an Assassin's left forearm, conceals the Hidden Blade with a series of metal plating arranged in formation for combat protection. As an Assassin was promoted through the ranks of the Order, his waist belt would also be upgraded to reflect the new found status. Altaïr and Malik both bore the highest level combat uniform in the Assassin's Order, with the most prestigious three-layer waist belts.

Desynchronization
Because Desmond lost Synchronization every time Altaïr was killed during combat, it is implied that Altaïr was never killed nor mortally wounded in armed conflicts or during assassinations. This would be feasible given his reputation as a legendary assassin of his time and his lineage.

Codex
Using the Apple of Eden Altaïr created the Codex pages as well as a new suit of armor for himself, one that was almost impossible to damage. This new armor would be passed down to each of his descendants, eventually being hidden away in the Sanctuary beneath the Villa Auditore.

Other Characters
Armor did appear on other individuals, and there were differences in the styles worn by guards in each city.

The guards in Damascus could be found in either lamellar, leather, or ringmail armor.

Guards in Acre could be seen in brigantine armor and chain mail, some complete with coifs.

Guards in Jerusalem were often found wearing scale or splintmail.

Each of these guard types could be found in the Kingdom near their respective cities.

The Knights Templar uniformly wore full suits of chain mail covered in a white tabbard with a red steel helm covering their face. All of the Knights Templar wore their signature red cross openly, whereas future Templars wore the cross symbol more subtly.

Italy
Ezio Auditore could purchase different types of armor from blacksmiths found throughout the game's various cities. There were four sets of armor that could be purchased, and a fifth - the Armor of Altaïr which could be gained through acquiring all of the Assassin's seals. Each set contained four individual pieces: chest plates, greaves, spaulders, and vambraces.

Statistics
Leather Armor was the first available armor and provided health bonuses but no resistance bonuses. Later Ezio could purchase Helmschmied, a variant of leather with metal inlays, Metal Armor and Missaglias, a stylized set of metal armor. Every armor after the leather set offers health bonuses and resistance bonuses. Armor could be damaged through combat or by falling from buildings so it was necessary to repair it at blacksmiths regularly. Each armor had a set number of circles that it could resist. In general twenty squares of combat or falling damage to the synch bar would remove one circle of resistance from every piece of armor one had equipped.

Altaïr's armor
Ezio could unlock Altaïr's improved armor by collecting the six Assassin seals from the tombs of six different Assassins. It consisted of black cloth with specially made armor integrated into it akin to the mythical properties of the Golden Fleece. As such the armor never required repairs. Page 19 of Altaïr's Codex revealed that this was the only suit made by Altaïr, who destroyed the written formula out of fear of the armor becoming widely used either by friend or foe alike.

Other Characters
All types of soldiers in Italy were armored to varying degrees, with archers as the lightest, followed by Agiles, regular soldiers, Seekers, and Brutes. Elite soldiers wear heavier armor than regular soldiers making them more resistant to Ezio's attacks and counter-attacks.

Rome
During the siege of Monteriggioni Ezio lost the Armor of Altaïr forcing him to run into battle clothed in a simple shirt, trousers and boots. Later on in Rome, Ezio's new robes and armor were anonymously given to him by Machiavelli. Ezio's newer attire resembled the clothes of Altaïr, with longer robes and a longer hood. Ezio's new armor came only with a spaulder and a single vambrace.

Ezio was able to purchase armor upgrades, just like in the previously visited cities, in a blacksmith shop. It was also possible to complete specific quests for the blacksmith shop on Tiber Island, in order to unlock parts of the Seusenhofer armor. The only set of armor that could not be purchased is the Helmschmied Drachen Armor (This armor's is available with the purchase of The Da Vinci Disappearance DLC).

Statistics
Armor designs in Rome had changed and were given metal inlays during the second and last set of purchasable armors. The Roman armor set was made of leather while the Rondelle armor set had the same design with metal inlays, the Plate armor was the unstylized with metal inlays of the Seusenhofer armor. When all six Keys of Romulus were obtained, Ezio was given the Armor of Brutus, an unbreakable armor.

Recruits
Ezio's Assassin Recruits could also wear armor; this was upgradeable as the assassin leveled up free of charge. A recruit started with no armor but could acquire leather pauldrons, leather greaves, a leather chest guard, and finally, a full set of plate armor (which replaced all the parts of leather armor already equipped). With 'level four' armor being the best recruits could have - they had more than double their original health, making plate armor extremely useful. Once the recruits reach the rank of Assassin however, they will have new robes (resembling that of Ezio's Master robes) and the armor of a full-fledged Assassin.

Other Characters
Guards were armored similarly those stationed in other Italian regions, with the addition of the Papal Guard as the most heavily armored opponents. Of the new guard archetypes the Crossbowmen were equal in defense to Archers, while Arquebusiers matched standard guards.

Constantinople
During Ezio's travels in Constantinople, he encountered a new variety of armor. From blacksmiths, he could acquire Azap Leather armor, the weakest, Mamluk Metal armor - stronger than the Azap Leather - and the Sepahi Riding armor, the strongest of the three. Additionally, upon initiating seven Assassin Recruits into becoming Master Assassins (doing the first part of every Master Assassin mission) he acquired the Master Assassin armor. After finding all ten of Ishak Pasha's memoir pages, he then journeyed inside the Hagia Sophia to obtain the Armor of Ishak Pasha.

Trivia

 * Ezio's initial spaulder in Rome is leather, while the cover art depicts him wearing a metal spaulder. His new hidden blade bracer was the same as it is on the cover, as well as his hidden blade. But like the metal spaulder, Ezio's second hidden blade does not appear like the one on the cover. Instead, it was a brown glove like his original second hidden blade used in the Assassin's Creed II E3 Demo, and also on pre-released Assassin's Creed II pictures. The second blade was originally displayed as an identical blade and bracer as his primary blade and bracer.
 * Vambraces for the second hidden blade can be bought at a blacksmith only when the second hidden blade is purchased from Leonardo, but none of the vambraces have the design of the bracer shown in the cover art.
 * The Armor of Altaïr and the Armor of Brutus both give 25 health squares without the need of repairs. However, in Revelations the Armor of Ishak Pasha and Master Assassin Armor only have a maximum of 20 health bars though they are still unbreakable.
 * With the Master Assassin armor equipped, Ezio's clothing color is returned to the default Original Grey. It will stay that way until you unequip the Master Assassin armor. It will still be possible to dye your clothes, however, this will not be noticeable until you unequip the armor. Additionally, like the Armor of Ishak Pasha,  the hood will remain on in cutscenes.
 * In Revelations, if you replay the second memory of the first sequence, any armor will be removed and will stay that way even after the completion of the memory.