Age of Empires II: The Conquerors Expansion (sometimes abbreviated to AoC) is the expansion pack to the 1999 real-time strategy game Age of Empires II. The Conquerors is the fourth installment of the Age of Empires series by Microsoft Game Studios and Ensemble Studios. It features five new civilizations (the Aztecs, Mayans, Spanish, Huns, and Koreans), four new campaigns, eleven new units, twenty-six new technologies, new gameplay modes, new maps and different minor tweaks to the gameplay.