Firearm

Firearms, or Guns, were a class of long-ranged weapons that launched projectiles at high velocity, through the confined burning of propellents. They were used as early as the late Middle Ages.

High Middle Ages
"The knowledge of projectile combat is not new to us, having been observed amongst our Eastern neighbors. But their weapons were much larger – and insufficient for our needs."

- Altaïr Ibn-La'Ahad's Codex, page 28.

Though he knew of firearms being used in ancient China, the Assassin Altaïr Ibn-La'Ahad took little interest in them, realizing that the weapons were of no use to his Order in their current size.

As such, upon obtaining the Apple of Eden, he successfully used the knowledge it held to miniaturize the design, "embedding their fiery weapon into a form that can be worn on the wrist."

Along with the formulation of a combustible powder that could be made from common ingredients, Altaïr kept the schematics for the hidden gun a secret available to only the Brotherhood's most trusted allies.

Sometime afterwards, he recorded all details of these in his personal journal.

Renaissance
In Italy during the Renaissance, another Assassin, Ezio Auditore da Firenze, came into possession of Altaïr's Codex, and showed the pages to Leonardo da Vinci. Leonardo deciphered the instructions, and was able to construct the hidden gun for Ezio's use.

Though firearms were uncommon until the early 16th century, after Cesare Borgia forcibly recruited Leonardo into his employ around 1499, the engineer was made to design a wheel-lock firearm, for use by the Borgia armies.

Cesare's ally, the French Baron Octavian de Valois, received a personalized, golden wheellock firearm from Leonardo, and kept it with him at all times. During the Fall of Monteriggioni, Cesare used this pistol to kill Mario Auditore.

A variety of firearms began to circulate among common guards as well, with Arquebusiers wielding long rifles or arquebuses, and with several Horsemen and Papal Guards using shorter pistols.

In later years, upon Ezio's travels to Constantinople, he encountered Turkish soldiers using Ottoman Flintlock Rifles, as well as Janissaries who used short pistols. The Assassins of the local guild also made use of firearms to guard the Assassin Dens.

American Revolution
By the time of the American Revolutionary War, firearms had become standard equipment for armies. Soldiers of both sides used muskets, often accompanied by.

The American Assassin Connor was able to wield a musket, as well as flintlock pistols.

Russian Revolution
During the late 19th and early 20th century, in the Russian Revolution, the Russian Assassin Nikolai Orelov wielded a modern bolt-action Mosin-Nagant rifle alongside the usual weaponry of his time.

Modern times
In 2012, Assassins continued to wield firearms in combat, and once used them on a direct assault on Abstergo Industries, in an attempt to rescue Desmond Miles.

Though Desmond overheard the exchanged gunshots over the intercom, Warren Vidic eventually told him that the rescue attempt had failed, and that most of the team had been killed.

Trivia

 * A number of firearms are available in Assassin's Creed: Project Legacy, including the arquebus, .303 SMLE, and M1917 revolver.
 * Owning two M1917 revolvers in Project Legacy grants the player the "Akimbo" achievement.