Arquebusier

Arquebusiers were firearm-wielding soldiers who served and protected the pontiff during their tenure. Similar to archers and crossbowmen, they patrolled rooftops, protected high profile locations, and guarded noteworthy targets.

Though Arquebusiers do not have as great a range as crossbowmen, what they lack in distance they make up in power; their rounds deal significant damage to both Ezio and his armor. Like crossbowmen, arquebusiers do not carry melee weapons. They will attempt to back up and resume shooting if engaged in close quarters combat.

Like all other guards, the color of their uniform indicate their allegiances; with red signifying them as soldiers of the Borgia, blue of French, and yellowish-green for those of Viana.

They were most notable during the assault on Monteriggioni, where armored arquebusiers under the command of Cesare Borgia were able to seriously wound Ezio Auditore in the shoulder and abdomen.

Aside from Borgia towers, arquebusiers usually can be found guarding the rooftops around the Pantheon and in the Castra Praetoria. They can also be seen patrolling the streets of the Antico or Campagna districts in pairs.

Trivia

 * If the player kills an arquebusier after he has turned hostile and thus draws his weapon, the gunman will drop his arquebus upon dying. However, there is no way to actually attain the relinquished gun, and - similarly to enemy Crossbows - the weapon will disappear shortly after moving out of the camera's view.
 * Some of the Borgia Tower captains behave exactly like arquebusiers.
 * All arquebusiers carry several bags across their belts, which likely contain gunpowder and lead projectiles for their arquebus, in case of having to reload in the heat of battle.
 * If the player, with his hands equipped, kills the arquebusier from behind, and the arquebusier falls off the building onto another building from a one story height, the arquebusier survives. If he lands on a building from two stories, he will catch himself, but he will be frozen. You can search him for items, but when you go to pick him up, he will be shown to be dead.
 * Similar to Papal Guards, arquebusiers are more often encountered during story missions.
 * The arquebusiers - after Papal guards and Brutes - are the third hardest enemies to find outside of story missions. Before the assassination of Octavian de Valois, a few French arquebusiers can be found on the towers outside the Castra Praetoria. Apart from that, they can be found on the rooftops around the Pantheon and two can be found patrolling a road in the Campagna and Antico districts.
 * Arquebusiers were originally supposed to look like militia guards with guns.
 * It is strange that arqebusiers have so much armour because all the other soldiers who use ranged weapons look like milita.

Source

 * Assassin's Creed: Brotherhood