Age of Empires II: The Conquerors is the first expansion pack to the 1999 real-time strategy game Age of Empires II: The Age of Kings. The Conquerors is the fourth installment in the Age of Empires series by Microsoft Game Studios and Ensemble Studios. It features five new civilizations (the Aztecs, Mayans, Spanish, Koreans, and Huns), four new campaigns, eleven new units, twenty-six new technologies, new gameplay modes, new maps and different minor tweaks to the gameplay. A second expansion, The Forgotten, was released exclusively on Steam in November 2013, over a decade since the release of The Conquerors. In November 2015, another expansion was released, also exclusive to Steam, entitled The African Kingdoms.