A contentious aspect of the game occurs in combat when a modern unit is fighting an obsolete or ancient unit. The ancient unit can sometimes win what most players consider to be an impossible battle.
The historian and anthropologist Matthew Kapell has published an essay critical of the Civilization series. It suggests that the game uses unique American myths of progress and the frontier in culturally elitist fashion.
Civilization has been one of the most popular strategy games of all time, and has a loyal following of fans. This high level of interest has spawned a number of free software versions, such as Freeciv and C-evo, and inspired similar games by other commercial developers, as well.