Multiplayer online battle arena (MOBA), also known as action real-time strategy (ARTS), is a genre of strategy video games that originated as a subgenre of real-time strategy, in which a player controls a single character in one of two teams. The objective is to destroy the opposing team's main structure with the assistance of periodically spawned computer-controlled units that march forward along set paths. Player characters typically have various abilities and advantages that improve over the course of a game and that contribute to a team's overall strategy. MOBA games are a fusion of action games, role-playing games and real-time strategy games, in which players usually do not construct either buildings or units.
The genre largely began with Aeon of Strife (AoS), a custom map for StarCraft where four players each controlling a single powerful unit and aided by weak computer-controlled units were put against a stronger computer. Defense of the Ancients (DotA), a map based on Aeon of Strife for Warcraft III: Reign of Chaos and The Frozen Throne, was one of the first major titles of its genre and the first MOBA for which sponsored tournaments have been held. It was followed by the two spiritual successors, League of Legends and Heroes of Newerth, and eventually a sequel, Dota 2, as well as numerous other games in the genre such as Heroes of the Storm and Smite.
The roots of the genre can be traced back decades to one of the earliest real-time strategy titles, the 1989 Sega Mega Drive/Genesis game Herzog Zwei. It has been cited as a precursor to, or an early example of, the MOBA genre. It used a similar formula, where each player controls a single command unit in one of two opposing sides on a battlefield. In 1998, Future Cop: LAPD featured a strategic Precinct Assault mode similar to Herzog Zwei, where the players could actively fight alongside generated non-player units. Herzog Zwei's influence is also apparent in several later MOBA games such as Guilty Gear 2: Overture (2007) and AirMech (2012).
In 1998, computer game company Blizzard Entertainment released its best-selling real-time strategy game (RTS) StarCraft with a suite of game editing tools called StarEdit. The tools allowed members of the public to design and create custom maps that allowed play very different from the normal maps. A modder known as Aeon64 made a custom map named Aeon of Strife (AoS) that became very popular. Aeon64 stated that he was attempting to create gameplay similar to that of Future Cop: LAPD's Precinct Assault mode. In the Aeon of Strife map, players controlled a single powerful hero unit fighting amidst three lanes, though terrain outside these lanes was nearly vacant.
In 2002, Blizzard released Warcraft III: Reign of Chaos (WC3), with the accompanying Warcraft III World Editor. Both the MOBA and tower defense subgenres took substantive shape within the WC3 modding community. A modder named Eul began converting Aeon of Strife into the Warcraft III engine, calling the map Defense of the Ancients (DotA). Eul substantially improved the complexity of play from the original Aeon of Strife mod. Shortly after creating the custom DotA map, Eul left the modding scene. With no clear successor, Warcraft III modders created a variety of maps based on DotA and featuring different heroes. In 2003, after the release of Warcraft III: The Frozen Throne, a map creator named Meian created a DotA variant closely modeled on Eul's map, but combining heroes from the many other versions of DotA that existed at the time. Called DotA: Allstars, it was inherited after a few months by a modder called Steve "Guinsoo" Feak, and under his guidance it became the dominant map of the genre. After more than a year of maintaining the DotA: Allstars map, with the impending release of an update that significantly changed the map layout, Guinsoo left the development to his adjutant Neichus in the year 2005. After some weeks of development and some versions released, the latter turned over responsibility to a modder named IceFrog, who initiated large changes to the mechanics that deepened its complexity and capacity for innovative gameplay. The changes conducted by IceFrog were well-received and the number of users on the Dota: Allstars forum is thought to have peaked at over one million.
By 2008, the popularity of DotA had attracted commercial attention. That year, The Casual Collective released Minions, a Flash web game. Gas Powered Games also released the first stand-alone commercial title in the genre, Demigod. In late 2009, Riot Games' debut title, League of Legends initially designed by Feak, was released. Riot began to refer to the game's genre as a multiplayer online battle arena (MOBA). Also in 2009, IceFrog, who had continued to develop DotA: Allstars, was hired by Valve Corporation, in order to design a sequel to the original map.
In 2010, S2 Games released Heroes of Newerth, with a large portion of its gameplay and aesthetics based on DotA: Allstars. The same year, Valve announced Dota 2 and subsequently secured the franchise's intellectual property rights, after being contested by Riot Games for the DotA trademark. In 2012, Activision Blizzard settled a trademark dispute with Valve over the usage of the DOTA trademark and announced their own standalone game, which was eventually named Heroes of the Storm. Dota 2 was released in 2013, and was referred to by Valve as an "action real-time strategy" game. In 2014, Hi-Rez Studios released Smite, a MOBA with a third-person perspective. Heroes of the Storm was released in 2015. Blizzard adopted their own personal dictation for their game's genre with "hero brawler", citing its focus on action.