Few games have been as influential as Sid Meier's Civilization (1991), which defined a new brand of strategy game covering an empire's technological, diplomatic, economic, and military endeavors over a huge expanse of time with very elegant gameplay that was easy to get into and keep playing, turn after turn. Civilization III marked a major update for the series, introducing new mechanics like culture, great leaders, and tradable resources, but the massive scale of the game remained the same. That's just what the upcoming expansion pack, Civilization III: Conquests, will change, with nine detailed "conquests," or scenarios, that zoom in on a specific moment in history. These scenarios can be nearly as involved as the main Civilization game with their own tech trees, additional civilizations, and unique units. Conquests also introduces a number of general gameplay enhancements that carry over to the core game and to the improved multiplayer modes.

Conquests features nine handcrafted scenarios set in specific time periods, from ancient Mesopotamia to World War II in the Pacific.

Firaxis and Breakaway Games have been working together on the expansion pack, and it's been in full production since January, not long after the release of last year's Play the World multiplayer-focused add-on. Yet the most involved of the scenarios, the Sengoku conquest set in feudal Japan, has been a Firaxis designer's personal project for more than a year. What makes the nine scenarios genuinely impressive is just how much the game is customized for each setting. The conquests are also designed to suit a variety of play styles, with some focused on culture or wonder victories, while others are about constant fighting over victory locations.

The scenarios are generally like compressed versions of the main game, and this has allowed the designers to put much more specific historical detail into each one. While the main game has long included anachronisms for gameplay reasons--like having the United States as a playable civilization starting in 4000 BC--much effort has gone into making even small details like World War II ship names authentic. The very earliest scenario appropriately takes place in ancient Mesopotamia and includes civilizations like the Babylonians and the Phoenicians, which aren't found in the main game. The scenario maps have been handcrafted to represent regional geography in some detail, and civilizations are placed in their historical locations. Although most players hurry through the ancient age in the main game to get to bigger and better things, the Mesopotamian episode has plenty of additions and balanced changes to create a real sense of progression from the Bronze Age to the Iron Age, with new structures (including the early factories, worker housing, and alchemist workshop), new technologies (like epic work projects), and government types like tribal council. Even though it's about a race to build the seven wonders of the world, there's plenty of reason to expand and build your empire to be the most powerful in the ancient world. In fact, it's essential to expand to control enough of the stone resource necessary to build wonders.

Each scenario is balanced individually, has its own tech tree, and can be as long and involved as the main game.

Another of the four episodes available in the preview version we played is a culture-focused scenario set in Mesoamerica. However, in the world of Aztecs, Incas, and Mayas, there's a new twist on how you can increase your cultural influence: ritual sacrifice. One of the additions to the game is the ability to capture enemy units, which are enslaved as workers and can be sacrificed if you choose. Seeing other nations' natives killed in public creates some amount of discontent among your citizens, but naturally if you run out of slaves to sacrifice and decide--in a desperate push toward victory--to send your own people to the altar, the discontent grows dramatically. The Mesoamerican map is also a good place to spot one of the new map features--volcanoes. They're easy to spot and can provide extra resources, but they will periodically blow their tops and wreak destruction, destroying units and cities within several tiles in a random direction.