Maybe you’re one of the millions of people currently enjoying Overwatch, Blizzard Entertainment’s multiplayer shooter. Or perhaps you’re an eSports fan, obsessed with League of Legends or Dota 2. Some of you have undoubtedly spent hours hunched over your phones, tapping away at Plants vs. Zombies or Clash Royale.
If so, you’ve got Warcraft to thank.
Players and critics liked the first Warcraft game. They loved the second, Warcraft II: Tides of Darkness, and the third, Warcraft III: Reign of Chaos. Its sci-fi spin-off, StarCraft, has been called the best video game ever made. Hearthstone, the digital Warcraft-themed card game, is becoming an eSports mainstay and has inspired numerous imitations. The Warcraft feature film even broke box office records in parts of the world.
The series’ success has made Blizzard into one of the biggest developers in the world. Before Warcraft, Blizzard made ends meet by programming ports of other people’s games. Now, the company holds an annual convention dedicated exclusively to its own intellectual properties.
That’s enough to cement Warcraft‘s legacy as one of the most important gaming franchises of all time, but the game’s influence goes beyond a catalog of spin-offs and Blizzard’s bank account. World of Warcraft, which turns Warcraft‘s fantasy setting into a virtual world populated by millions of real-life players, defined the MMORPG genre. Oh, and the $700 million esports industry? Without Warcraft, it wouldn’t exist.
It all started in 1994, with Warcraft: Orcs and Humans. Warcraft wasn’t the first real-time strategy game—the genre has been around in various forms since the 1970’s, and there’s a lot of Westwood Studios’ Dune II in Warcraft‘s DNA. As in most strategy games, Warcraft players collect resources, which they use to build armies. When their forces are big enough, players send their troops out into the wilderness to conquer enemy bases. The first side to wipe out its opponent wins.
Warcraft‘s basic gameplay was similar to its predecessors, but Warcraft added a streamlined user interface and a compelling storyline, making the game more accessible. New mission objectives, like ending sieged towns and assassinating specific targets, injected some variety into real-time strategy’s well-established formula. Warcraft is full of character and humor, too, which lends some personality to the game’s nameless grunts.
However, Warcraft‘s biggest innovation was its multiplayer mode. Pre-Warcraft, most strategy games were solitary affairs. Warcraft changed that. Using a dial-up modem or a local area network, players could connect to each other’s PCs and compete against one another instead of computer-controlled opponents. Warcraft wasn’t the first real-time strategy game to offer online play, but it was the first one to hit the mainstream, and before long, multiplayer combat was real-time strategy’s main draw.
Multiplayer was even more important to StarCraft. Initially, StarCraft wasn’t much more than Warcraft with a sci-fi skin. Patrick Wyatt, Blizzard’s former Vice President of Research and Development, describes the first version of StarCraft as “Orcs in space.” It ran on the same code as Warcraft II, and was created as a quick, one-year project designed to bridge the time between Warcraft II and Blizzard’s upcoming role-playing game, Diablo.
After StarCraft received a lukewarm response at E3, Blizzard rebooted the project, writing a new engine from scratch and expanding the game’s scope. When StarCraft finally came out in 1998, Blizzard had Battle.net, its proprietary online matchmaking service. With features like filters and leaderboards, Battle.net made it easy to connect with StarCraft players around the world, and competition thrived.
StarCraft received rave reviews, and tens of thousands of players flocked to Battle.net. The game was especially popular in South Korea, where third-party organizers started to hold tournaments. The competitions attracted spectators, the best players eventually became celebrities who earned massive salaries, and before long, the modern eSports model was born.
But StarCraft was just the beginning. When Warcraft III: Reign of Chaos came out in 2002, it shipped with both a single-player campaign and online Battle.net support. It also came with a piece of software called World Editor, which let fans change almost every part of the game.
Previous editions of Warcraft included map editors, but World Editor took things further. With the new mode, ambitious players could take the Warcraft engine and use it to create entirely new games—and that’s exactly what they did.
Thanks to World Editor, tower defense games became incredibly popular, paving the way for hits like Plants vs. Zombies, PixelJunk Monsters, and Bloons TD 4. However, the most important type of game created in World Editor is the multiplayer online battle arena, or MOBA. In 2003, a player who used the online handle Eul ported a StarCraft map called “Aeon of Strife” into Warcraft III. He called the new game “Defense of the Ancients,” and it changed everything.
In normal Warcraft, players control an army. In Defense of the Ancients, players control a single character. Ten people—two teams of five—play at the same time, trying to conquer the map and destroy their enemies’ base, while preventing their opponents from doing the same. Different characters have different abilities, and strategy and teamwork are crucial if you want to survive.
Defense of the Ancients quickly became Warcraft III‘s most popular modification, and DotA games dominated Battle.net. Using World Edit, players all over the world started creating their own Defense of the Ancients maps, characters, and items. Eventually, two modders, Meian and Ragn0r, combined the best of these enhancements into one map and called it DotA Allstars, which quickly became the standard version of the game.
Dota is free for Warcraft III owners, but that didn’t stop developers from trying to capitalize on its success. In 2009, Riot Games hired Steve “Guinsoo” Feak, one of DotA’s primary engineers, to help develop its DotA-inspired strategy game, League of Legends. Around the same time, an anonymous modder known as IceFrog defected to Valve Software to work on Defense of the Ancients’ commercial sequel, Dota 2.
The rest is history. MOBAs went on to become the biggest genre in eSports, and League of Legends and Dota 2 are at the top of the heap. In 2015, The International—Dota 2‘s annual tournament—offered a prize pool worth over $24 million, the biggest ever for an eSports competition. Meanwhile, League of Legends is one of the most-played games on the planet, and earns Riot Games $150 million in revenue every month.
None of this happened in a vacuum, of course. Before World of Warcraft, there was EverQuest and Ultima Online. Magic: The Gathering predates Hearthstone by 20 years. Game tournaments have been held since arcades’ heyday in the early 1980s. Warcraft and its progeny may not introduce radical new ideas to the gaming landscape, but under Blizzard’s stewardship, they often refine and codify what’s already out there, ultimately coming to define industry standards. We might still have eSports without Warcraft, but they’d look awfully different.
And the most exciting part? Blizzard is just getting started. On the film side, Warcraft‘s performing well enough in foreign markets that a sequel seems inevitable, sparking perhaps the first successful video game movie franchise in history, while World of Warcraft‘s sixth expansion, Legion, arrives later this summer. It’s hard to predict where gaming is going to go in the future, but no matter which direction it takes, expect Warcraft to be a big part of it.
Christopher Gates is a freelance contributor.
This article originally appeared on June 29, 2016.