Unlike in previous games, barbarians will advance in technologies beyond the Medieval Era, being capable of producing units equal to that of what the most advanced civilization can produce at the time. This is especially true if Raging Barbarians is turned on, with hostile barbarians being produced with new technologies almost the turn the first civilization finishes researching it. It may be theorized that these aren't old-fashioned barbarians anymore, but rather bandits...or in the later eras, "freedom fighters", terrorists, or drug cartels.
Behavior and Activities
Barbarians in Civilization V are unlike the ones in Civilization IV, in the sense that they do not make cities like civilizations can - their "cities" are their encampments, which produce only military units. The rate of encampment creation depends on the difficulty level, becoming greater on higher difficulties. It is increased even further if the option Raging Barbarians is selected.
Barbarians are always hostile to all civilizations and city-states, and will spawn fighting units in each encampment until it is destroyed. Encampments appear with a unit already in them, and all subsequent units created will start roaming the lands immediately (unless the encampment has been left undefended for some reason, in which case the new unit will stay right in the encampment). Unlike civilization units, barbarian units do not use up strategic resources, so they can produce any base land unit, and many naval units, regardless of their typical cost.
Possible barbarian units include the ones unavailable to any playable civilization, such as the Brute (which has the same strength as a Warrior) and the Hand-Axe. Encampments located on a coastal tile also have the ability to produce Galleys and other naval units.
The barbarians' main activity is harassing cities. They will move in and try to pillage improvements, attacking the most important ones first (those accessing a luxury resource, for example). If injured, they have the ability to heal every time they pillage an improvement. With enough units nearby barbarians will begin to attack cities; if brought to zero HP, a city will be pillaged and may lose Gold, Population, and buildings.
Barbarians also go after civilians and try to capture them (by moving into the same tile they occupy). Captured civilians are then moved to the nearest encampment, where they are held captive until someone clears the encampment. The civilian unit is then freed, and if the captured civilian did not originally belong to the player who clears the encampment, they get to choose whether to take it for themselves, or return it to its original owner (which will net a nice boost in diplomatic relations with their leader).
Barbarian units roam the countryside (and the seas), all the time, attacking at will. However, they won't attack stronger units, or ones that are currently in a strong position (such as on a hill or fortified). When there are multiple targets, they usually attack the weakest unit, taking into account their health. There will be one barbarian unit at each encampment at all times, guarding it in a fortified stance. Depending on the difficulty setting, though, this unit may go out a short way to make an opportunistic attack or capture an unwary civilian unit.
Finally, in Brave New World, barbarians will also try to pillage any trade route they can reach. The route is immediately terminated and, what's even worse, the trade unit that was on it is captured and turned into a new barbarian unit! This could have results ranging from purely annoying to near-disastrous, especially in the early game.
Earning Experience When Fighting Barbarians
Units earn experience normally when fighting barbarians, but they can't earn more than two promotions through that experience. This means that fighting barbarians can be a good source of experience for units early in the game, but later on, when they've earned many promotions, or when new units are constructed with two promotions, barbarians become more of an annoyance than an opportunity.
It is very important to defend against barbarians, especially during the early game - they, rather than other civilizations, will usually be the main danger in this period. Always try to keep a military unit in every city, keep it alert for roaming barbarians, and move it to protect Workers and improvements when they are spotted. When moving Settlers, it is safest to move them together with a military unit. Get ranged units as soon as possible to start clearing encampments safely.
Usually, units enjoy a combat bonus against barbarian units. This bonus, however, diminishes almost to nothing at the higher difficulty levels. The bonus can be increased at all levels by adopting the Honor Social Policy, which gives units an additional bonus against barbarians. Also, civilizations with this Policy will gain a fixed amount of Culture points per each barbarian unit killed (based on the Combat strength of the unit).
Certain special abilities allow civilizations to "convert" barbarians to their side. Germany has a chance to get barbarian units to join, if they are defeated while defending their encampment. Similarly, the Ottomans have a 50% chance to recruit a barbarian naval unit (and earn Gold) by moving a ship next to it. While city-states react to this as if the barbarian unit was destroyed, no Culture will be earned even if the Honor policy tree is active. For the Aztecs, which gain Culture for every enemy killed, activating the Honor tree doubles the Culture gained. In Brave New World, the Reformation Belief "Heathen Conversion" allows Missionaries to convert Barbarian units if they are adjacent.
After trade routes are established, be on the lookout for barbarians near the route. In the beginning of the game a lot of land remains unexplored and dark, which is the ideal situation for spawning barbarian encampments. Their units can pillage a route before anyone is aware of the threat - they can even turn a land trade unit into a mounted barbarian unit. So, unless otherwise occupied, dedicate a couple of units to patrol between the source and target city of the trade route.
City-states will occasionally post seek-and-destroy quests against barbarian encampments in the early game. Try to complete them, because of all quest types they give the largest single influence boost, and are an easy way to make friends (and even allies) with city-states. To do this, try to form a task force of one melee and one ranged unit. Move them to the more distant city-states; destroy those encampments closer to home territory with the units guarding the cities. Barbarian encampments are often pretty close to civilized territory, so when one is discovered, friendly units may be in a good position to attack it. Wait until a city-state marks it with a quest, or destroying the encampment will not yield any influence. If other civilizations have military units nearby, they may swoop in and seize the encampment after it has been weakened by a turn or two of attacks. If this happens, the Gold reward and Influence boost will go to them. It is especially annoying, for example, when your ranged unit finally kills the Barbarian defending an Encampment only for another civilization's Scout to walk in and collect the prize before you can. Try to avoid this by blocking them as much as possible, or if necessary, waiting until they leave the area. However, know that nearby city-states may themselves resolve to attack the Encampment after many turns have passed without anyone taking care of it.
- Even when the "No Barbarians" option is turned on, a raiding party of three Barbarian mobile units can spawn if the Unhappiness in a civilization is above 10.