Sid Meier's Civilization IV: Warlords added many new features to the original game. These include:
- A new category of Great People known as "Great Generals";
- The ability to institute vassal states;
- Eight new scenarios
- Six new civilizations playable in single-player and multi-player;
- Ten new leaders (including new leaders for existing civilizations);
- Three new leader traits (Charismatic, Protective and Imperialistic);
- Unique buildings for each civilization;
- Three new wonders;
- New units, resources, and improvements;
- Core gameplay tweaks and additions;
- Inclusion of all patches released for original Sid Meier's Civilization IV.
The game introduces a new type of "Great Person" unit, known as a Great General. Great Generals are usually created when the total experience earned by a civilization's military units against other civilizations reaches specified thresholds, rather than Great Person points generated by its cities. In addition, the civilization that acquires the "Fascism" technology first receives a free Great General. A Great General can be used similarly to other Great Persons: to join a city as a "Great Military Instructor", which gives +2 experience points to any military unit created in the city, or to create a Military Academy, which permanently boosts military unit production (by +50%) in the city. The Great General can also be attached to a military unit forming a joint unit led by the Warlord, sharing 20 experience points with all units in its square and giving the Warlord unit free upgrades and exclusive access to special promotions. In all normal games and most scenarios, a destroyed Warlord unit is lost permanently. However, in the Alexander and Genghis Khan scenarios, the title characters serve as Great Generals, and if either is lost, he will be reborn in his civilization's capital city after several turns.
The new Vassal States feature allows players to take up other empires as "vassals," the game's equivalent of protectorates. When an empire becomes a vassal, it loses the ability to declare war and make peace independently, and may be called upon to pay "tribute" in the form of game resources to its "master" (suzerain) state in return for the promise that its master will protect the vassal. Players can use Vassal States to achieve a Domination Victory, since half the vassal's land and population count towards a domination victory for the master, but not vice versa. Similarly, if the master goes to war with another civilization, the vassal too has to go to war. However, other countries' opinions of you will worsen if you have a vassal they dislike. The vassal may still reject trades for gold and technologies.
During peacetime, civilizations can offer their vassalage in return for protection from an enemy, but it may be ended if the state's relative land and population statistics change. Vassal agreements signed in a state of mutual war, as part of a peace treaty, are considered capitulation and bind both parties. The agreement is terminated, however, if the vassal acquires 50% more land area than the master or the vassal loses half of the land it held when the agreement was signed. The only way a master can terminate the agreement is if the vassal refuses to pay tribute. The master can then choose to declare war.
In order to make the civilizations more distinctive, every civilization has received a "Unique Building". These unique buildings replace the standard buildings, and grant special advantages.
New civilizations include Carthage, the Celts, Korea, the Ottoman Empire, the Vikings, and the Zulu. Four new leaders are introduced for existing civilizations. Three new leader traits are introduced, and many existing leader traits have been changed.
Two new buildings, three new units, and three new Wonders of the World have been added. Each civilization also has its own unique building, replacing a standard building and granting additional benefits.
- Peloponnesian Wars: After vanquishing the Persian invasion in 480 BC, tensions between Athens and Sparta lead them to compete for ownership of the Greek world in 444BC. The Athenians start with a strong economy and mastery of the sea, but their empire is far-flung. The Spartans have few overseas possessions but a powerful land army. Both sides have multiple city-state allies, represented as vassal states.
- Chinese Unification: This scenario puts the player in charge of one kingdom, seeking to defeat six rival kingdoms of the Warring States Period to gain control of China. Bloodlines replace religions as a measure of influence that can be spread via emissaries in the same way as missionaries in the original game. An "Emperor's Council" wonder allows a vote-determined victory (similar to the UN in the regular game) as an alternative to outright conquest.
- Alexander's Conquests: In this scenario, the player controls both the Macedonian forces and Alexander himself, represented in the game as a special Great General unit who cannot die in battle (instead being "wounded" for a few turns). The technologies for this scenario are all military and give benefits to units in the field. Finally, the civics menu is replaced with a series of titles (ranging from "Alexander the Upstart" to "Alexander the Great") which will aid the player in their conquest.
- The Rise of Rome: In 300 BC, the powers of Rome, Carthage, Gaul, Greece, and Egypt compete for ownership of the Mediterranean. Special resources that can provide "victory points" are distributed next to each of the AI controlled starting capitals. Leaders in this scenario each have three traits instead of two, and multiple upgrades for military units can be researched.
- Vikings: The player plays as Ragnar Lodbrok, ruler of the Vikings, and has to organize massive, loot-gathering raids on England, Ireland, and Northern Europe. The goal of this scenario is to amass a certain amount of gold (which varies according to difficulty level) within 200 turns. Money can be earned by sacking cities, ransoming captured cities back to their original owners, and by researching the location of treasures and bringing them back (in the form of a special treasure cart unit) to the Viking capital.
- Genghis Khan: The player controls the Mongol hordes as they attack Asia. Without a starting city, the Mongolian civilization have special "camp" units, that are similar to settlers but when deployed will automatically spawn different types of units, depending on the terrain type occupied. The goal of this scenario is to accumulate "victory points" by capturing or destroying enemy cities, destroying enemy units, and pillaging improvements. The player steadily loses points over time (based on difficulty level), and must aggressively earn new points to avoid going negative and losing the scenario. The technology tree for the Mongols in this scenario is radically different from the original Civilization IV technology tree; each of the 15 enemy civilizations represents a technology that can be earned by the Mongols by either capturing two of that civilization's cities, or by vassalizing that civilization.
- Omens, 1754: In an alternative history portrayal of the Seven Years' War, the player must race to colonize the Ohio River Valley while playing as either Marquis Duquesne of France, or George Washington in the service of Great Britain. The main conflict is a religious one between the French Catholics and the English Protestants with the native Lenape civilization caught in the middle, and the goal of the scenario is to gain religious influence. The scenario also has a supernatural element, in which the forces of Divinity appear at various times to punish the less-pious and ultimately to declare a winner.
- Barbarian Horde: The player takes control of the barbarian state, whose aim is to destroy all other civilizations on a randomly-generated map. In this scenario, cities are rendered uncapturable; instead, if a barbarian unit enters a city it is razed, providing gold with which further units can be produced. The Barbarians have a camp similar to the one in the Genghis Khan scenario, at which purchased units will appear.
Sid Meier's Civilization IV: Warlords includes new music and also features older music directly from Sid Meier's Civilization III and Sid Meier's Civilization III: Conquests, which augment the game's existing ancient and classical era music that had relatively few selections. The new opening theme is an Lebanese love song entitled "Al Nadda".
- Sid Meier's Civilization IV: Warlords on Steam
- Official Sid Meier's Civilization IV: Warlords website
- Civilization IV: Warlords Info Center @ civfanatics.com