Age of Empires II: Age of Kings has thirteen playable factions, all of which have their own unique traits, particular advantages and disadvantages, as well as a single unique unit. Here is a list of the factions, including some tips on how to use their strengths to the best effect.
Britons: favoring bowmen supported by heavy infantry, the Britons do best to fight at a distance. The Briton longbowman is, by far, the best ranged unit in the game.http://aok.heavengames.com/gameinfo/civilizations#britons
Byzantines: with the best tech tree and defensive buildings in the game, the Eastern Romans of Byzantium prefer to fortify their bases before attacking. http://aok.heavengames.com/gameinfo/civilizations#byzantines
Celts: the wild Celts have excellent assorted infantry, but with few cavalry units or defensive structures they're vulnerable to more 'advanced' civilizations. They do have excellent siege weapons, however. http://aok.heavengames.com/gameinfo/civilizations#celts
Goths: the old invaders of Rome have strong infantry and cavalry, but few archers. It's best to train lots of cheap infantry, especially the Huskarl and overwhelm opponents. http://aok.heavengames.com/gameinfo/civilizations#goths
Teutons: the Teutonic Knight is the best infantry unit in the game, and along with a superb tech tree and a great mix of cavalry and archers, the Teutons dominate in the later ages of the game. http://aok.heavengames.com/gameinfo/civilizations#teutons
Franks: with their signature throwing axes and the best cavalry in the game, the Franks like to fight in close, with some cannons to take out towers and castles. Beware the Briton longbow, however. http://aok.heavengames.com/gameinfo/civilizations#franks
Mongols: the Mongols love to move, using their horse archers to run circles around slower infantry units. http://aok.heavengames.com/gameinfo/civilizations#mongols
Chinese: with a population bonus and the cheapest infantry around, the Chinese overwhelm their foes with numbers. http://aok.heavengames.com/gameinfo/civilizations#chinese
Japanese: an island culture, the Japanese have the strongest navy and the best bonuses for fishing and unit transport. They lack strong cavalry, however. http://aok.heavengames.com/gameinfo/civilizations#japanese
Persians: with mighty war elephants and powerful heavy cavalry, the Persians like to charge with a few strong expensive units, or just hide behind their strong walls. http://aok.heavengames.com/gameinfo/civilizations#persians
Saracens: favoring the camels of their desert homes over horses, the Saracens like to attack quickly and then retreat behind heavy fortifications. http://aok.heavengames.com/gameinfo/civilizations#saracens
Turks: gunpowder is the Turkoman's weapon of choice, and with the best assortment of cannons and gunpowder units of any faction, the Turks can become very deadly late in the game. http://aok.heavengames.com/gameinfo/civilizations#turks
Vikings: with longboats for fast attack from the sea and the dreaded Beserker heavy infantry for land battles, the Vikings are best when on the offensive, though they lack good horse and siege units. http://aok.heavengames.com/gameinfo/civilizations#vikings
Series
The second game of the Age of Empires series, Age of Empires II: Age of Kings advanced the gameplay and depth of the original Age of Empires with more units, more factions and additional campaigns. The game was a monumental success and was followed by the stand-alone Age of Mythology and the next in the series, Age of Empires III.
