Age of Empires II: The Age of Kings is a real-time strategy (RTS) video game developed by Ensemble Studios and published by Microsoft. Released in 1999 for the Microsoft Windows and Macintosh operating systems, it was the second game in the Age of Empires series. An expansion, The Conquerors, was released in 2000. A PlayStation 2 version was released by Konami in 2001, and a Nintendo DS spinoff, Age of Empires: The Age of Kings was developed by Backbone Entertainment in 2006. A Dreamcast port, by Konami, was canceled.
The Age of Kings is set in the Middle Ages and contains thirteen playable civilizations. Players aim to gather resources, which they use to build towns, create armies, and defeat their enemies. There are five historically based campaigns, which constrict the player to specialized and story-backed conditions. There are three additional single-player game modes, and multiplayer is supported. Despite using the same game engine and similar code to its predecessor, development of The Age of Kings took a year longer than expected, forcing Ensemble Studios to release Age of Empires: The Rise of Rome in 1998 instead. The design team focused on resolving significant issues in Age of Empires, but noted on release that some problems remained.
Reception of The Age of Kings was positive. The significant number of new features was praised, as were the gameplay improvements. Some reviewers were critical of the presentation of units—they were seen as bland and uninteresting—while others considered The Age of Kings to be overly similar to its predecessor, Age of Empires. Three months after its release, two million copies of The Age of Kings had been shipped, and it topped sales charts in seven countries. The game won multiple awards and has had a significant impact on future games in its genre. Both the original Age of Empires II and the expansion pack were later released as "the Gold Edition".
In April 2013, Age of Empires II: HD Edition was released on the Steam digital distribution platform for Windows operating systems. The HD Edition includes both the original game and the expansion The Conquerors, as well as updated graphics for high-resolution displays. It also supports user-generated content through the Steam Workshop and multiplayer games provided through the Steam servers. On August 16, 2013, Microsoft announced The Forgotten, the first new expansion in nearly 13 years and exclusive to the HD Edition. On April 15, 2015, developer Ryz0n announced a new expansion for the game, focusing on Africa.