First expansion for top strategy series will have military focus, introduce six new scenarios, new units, and new civilizations. By Tor Thorsen , GameSpot

Since it was released last October, Civilization 4 has never fallen off NPD Funworld's weekly list of top 10 best-selling PC games, selling over a million copies. The latest installment in Firaxis' long-running strategy series was also singled out by Firaxis owner Take-Two Interactive as being one of its best-selling titles during its last financial quarter.

Hoping to further capitalize on Civilization 4's success, Take-Two subsidiary 2K Games announced today that it will soon release the game's first expansion pack. Titled Civilization 4: Warlords, the expansion "pays homage to some of history's greatest military leaders." Though no Hannibals, Khans, Napoleons, Lees, Rommels, Pattons, or Schwarzkopfs were mentioned, the game promises the introduction of new Warlord units that will help turn the tide of battle in players' favor.

As has been the case with other Civilization expansions, Warlords will introduce a bevy of new units, resources, leaders, civilizations, and wonders of the world. However, 2K Games' announcement did not mention anything specific, other than that there would be "six new scenarios" that give players "the chance to change the course of history."

As yet unrated and unpriced, Civilization 4: Warlords will be released this summer. It will require the original game , which was named GameSpot's Best PC Game of 2005 , to play.

Mar 16, 2006