Notable features

This campaign depicts various conquistador armies that travelled to the New World by spawning large, formidable armies in the Americas with allegiance to the Spanish. Once spawned, the Spain faction can use these armies however they see fit. French and English forces will show up in the same way: the French appear in Louisiana and the English in Honduras.

These conquistador forces are made up of limited numbers of expensive but formidable European units, who are frequently supplemented by local native mercenaries. The native factions have weaker units with limited armor, but their incredibly inexpensive upkeep allows them to field a large number of them, and they often have high morale.

When the player progresses through the campaign playing as New Spain, the player will be presented with missions from the King of Spain, and when sufficient influence is gained, the player may be granted a higher title of nobility such as Baron, Count, etc. These titles unlock more advanced building levels for the player to use.

The Apachean Tribes faction has access to the "warpath" ability, which is a shamanistic counterpart to the jihad in the main campaign. The Apache can also learn from the technologies of European factions—after battling a European faction such as New Spain, the Apache will be able to construct gun trading tipis and horse trainers, unlocking new, more technologically advanced units (such as cavalry and musketeers, which the faction initially lacks). The Chichimeca can also use enemy technology to their advantage.

All of the factions adhering to the "Sun God" religion are able to sacrifice units instead of disbanding them. They can also sacrifice populations upon capturing a settlement or they can sacrifice captured enemy troops. Sacrificing upholds the religion of the Sun God and increases the happiness of the local populace.

Notable features

The campaign map features the presence of permanent stone forts placed in strategic locations, which can be garrisoned and provide free upkeep for a small number of units. These structures can hold out for a brief time against sieges and are automatically repaired after each battle.

Certain units can only be trained if that faction's culture is high enough in a settlement, making expansion into conquered land more difficult. As all factions are Catholic, culture has replaced religion in the campaign and priest units are unavailable.

A special, unplayable faction—the Barons' Alliance—is similar in gameplay terms to the Eastern and Western Roman Rebels from Rome: Total War: Barbarian Invasion. When characters, armies and settlements under English control rebel, they will become part of the Baron's Alliance, a faction with essentially the same strengths and weaknesses of the English faction, including the ability to utilise diplomacy and agents to achieve their goals.

Every faction gets paid an additional amount of florins every turn. This payment is referred to as "the King's Purse". In Medieval II: Total War, some factions had a high king's purse payment and some had a low payment. Rather than having a fixed king's purse, each faction in the Britannia Campaign has a dynamic king's purse—the sum of money a faction is paid every turn can change.

A number of special historical figures, including King Edward I, William Wallace, Prince Llywelyn ap Gruffudd, High King Brian O'Neill and King Haakon IV of Norway, appear either at the start of the campaign or at some later point. Though they lack the special abilities of the hero characters from the Crusades campaign, they usually possesses unique traits and are accompanied by a large army.

If any of the starting Welsh settlements are captured by the English, Welsh insurgents rise up in an attempt to recapture the settlements. The quality of the units in the rebel army will depend on which settlement is captured—for example, the rebel army will be very strong if the starting Welsh capital—Caernarvon—is captured, and it is a weaker army if smaller Welsh settlements, such as Pembroke, are conquered. A notable historical inaccuracy in this respect is that Caernarvon, the Welsh capital, did not have a castle until 1283, despite the campaign beginning in 1258, and was no more than a minor town at the time. The actual capital of Wales in the period, Abergwyngregyn, is not represented in the game.

Notable features

Generals in the Crusades campaign have the ability to construct permanent forts that remain even after vacated by troops.

The Principality of Antioch and Kingdom of Jerusalem may make use of the Knights Hospitaller and Knights Templar, respectively, thus giving them access to unique units - of whom only one of each may be present on the campaign map at one time.

Each of the five playable factions owns a single region designated as a "Power Centre", with the loss of these centres dealing a major blow to that faction. For example, the loss of a faction's Power Centre will prevent the recruitment of certain troop types. Should a Power Centre be lost, reinforcements will often be sent to assist in recapturing that settlement.

In addition, there are some events that can aid or hamper the player's faction. Namely, some of these are the Fourth Crusade (the arrival of two large Venetian armies near Constantinople, which can threaten the Byzantine player), the Mameluke rebellion of 1250 (when the Mamluk dynasty seized power in Egypt, giving the player a powerful Mamluk army under Baybars), the Mongol invasion of Asia (which can prove threatening to any player), and the rise of Osman I, which gives the Turks a reformed army called Janissaries.

Notable features

Crusading nobles, drawn to the conflict against Paganism in search of fame and glory, will request the assistance of the Teutonic Order in return for donations to the Order's coffers. The size of the donation varies depending on the nobles' successes. The Lithuanian leader will be rewarded by his council of nobles in events should he manage to kill any of these crusaders.

When playing as Denmark, it is possible for the player to form the Union of Kalmar. In order to do this, the player must first take the Scandinavian settlements of Kalmar, Göteborg, Visby, Uppsala and Åbo. After taking control of these settlements, the player must then kill the Norwegian king, either through assassination or a direct battle. If the entire Norway faction is eliminated, it is impossible to form the union. After forming the union, Denmark will take on a new banner, gain access to all the existing settlements and armies of Norway, and unlock the ability to build three new units.

Early in the campaign, an event will herald the formation of the Hanseatic League. The League consists of five specific regions on the campaign map—Hamburg, Danzig, Visby, Riga and Novgorod—which represent the group's most important assets. The faction controlling the most of these settlements has the greatest chance ^{[citation needed]} to be offered the option of building the Hanseatic League Headquarters, a unique building that provides significant financial rewards.