This new Capital won't matter to your victory, you need to conquer the original. The replacement Capital of the victim Civ gets the bonuses of a Capital, but can be razed unlike a normal Capital City.

Only the original counts, meaning that if any other player has lost their Capital, you must take it back from its new owner through War or Diplomacy. To win, you must control all original Capital Cities. The Victory Screen will show who controls each of the original Capital Cities required for Domination This notice will be removed when the Civilopedia is updated. The original requirement stands for people without DLC, but with Brave New World you will need to control all original Capital Cites. This Guide's description of the condition is accurate and the Civilopedia will be eventually updated with a patch. At present, the Civilopedia is incorrect in stating the victory requirement and lists the original. This Guide will offer tips and strategies to help you win the world through war and capturing Capital cities while keeping your own Civ happy and productive. Now you must control all original Capital cities to earn the victory, and it's a much better system overall. This led to some cheap victories that could even happen on accident if opposing Civs have been at war. Once upon a time, you only needed to be the last player controling your original Capital.

The Domination Victory requirements of Civ 5's Brave New World have received a much-needed upgrade since the initial release of Civilization V.

Civilization 5 Domination Victory Winning by Capturing all Capital Cities in the Brave New World DLC Civilization 5: Brave New World Domination Win

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