Since the number of pawns in a civilization is (usually) fixed, and can only go down as other civilizations capture territories, eventually a civilization will reach a maximum number of territories that it can support. At the beginning of any turn, the player owning that civilization can declare that it is going into "decline". This allows the player to select a new civilization and bring that onto the board while the pawns of the former civilization remain in place, no longer movable but continuing to gather points until their territories are captured.