A city must have iron in its Strategic Resource box to build a Samurai.
Similar to the European knights, Japanese samurai were landowners who volunteered military service in exchange for a larger warlord's protection. Their handsome lacquer armor gave them durable protection on the battlefield. The warrior code of "Bushido" placed exacting restrictions on their behavior, both on the field of battle and off. One such tenet was that samurai of opposing forces must seek each other out and battle one on one. While their armor provided some safety from early gunpowder weapons, soon more advanced weaponry and skilled marksmen relegated them to administrative and leadership roles. The samurai caste was abolished in 1868.