In late 2007, something special happened in the world of the first-person shooter. After four years of development, the teams behind the world's most popular FPS franchise, Call of Duty, revolutionized the multiplayer aspect of the series with the release of Call of Duty 4: Modern Warfare. Previously focusing on World War II scenarios, Modern Warfare's scene was present-day and was the first in the series to earn a mature rating. Now, nine years later, millions of casual fans across the globe still play Modern Warfare. But one thing has changed for the Call of Duty development team: esports.

What was once considered as a minority and organized by third-party tournament organizers, the Call of Duty esports scene has now become a prized jewel of the community. This year, Activision along with PlayStation -- the game's official competitive console -- and esports tournament organizer ESL, launched the Call of Duty World League, a two-part competitive league that takes place over the spring and summer.

For Jay Puryear, the director of brand development at Treyarch, one of the three studios that develops Call of Duty and the minds behind the most recent installment, Call of Duty: Black Ops 3, the passion behind the competitive Call of Duty esports community is what matters most.

"I think the fans and the passion of the esports community really comes from the heart," Puryear told ESPN esports this week at the Electronic Entertainment Expo in Los Angeles. "Because they are so educated and they're passionate, they appreciate what they're watching more than just the common fan who turned it on to take a look at it. They've always been very respectful, they're passionate, they have their beliefs and let you know what they like and what they don't like. We really try at the studio level, as well as with the Call of Duty World League, to really just listen to that."

"I think that the biggest thing for [the players] is that they just want to play. It's up to us to make sure we give them as many venues and avenues in which to play and participate in Call of Duty World League." Jay Puryear, Treyarch director of brand development

Compared to the massive League of Legends and DOTA 2 communities, as well as its biggest competitor, Counter-Strike: Global Offensive, competitive Call of Duty is one of the smaller esports. But despite a minority of viewership on platforms such as Twitch and MLG.tv, Call of Duty launched the World League in January, with its first season wrapping up in March. Activision will bring the second Call of Duty Championships to its user expo, Call of Duty XP, this fall culminating Sept. 2-4 in Inglewood, California.

Each stage of the Call of Duty World League features massive prize pools in the North America and Europe divisions ($250,00 for NA, $200,000 for EU), and will award $150,000 in Australia and New Zealand (considered one region, ANZ). Such a major investment is a big leap for a publisher that before this year did not commit to regular competition.

"I think the [reception of Call of Duty World League] is very, very positive," Puryear said. "I think there are a few things that early on, we wish we could have more LAN [offline] events for [the players] for Stage 1. But for Stage 2, we're gonna have one in June, July, August and September. ... I think that the biggest thing for [the players] is that they just want to play. It's up to us to make sure we give them as many venues and avenues in which to play and participate in Call of Duty World League."

As an American-based company and Call of Duty's critical acclaim in North America, Activision has primarily held events in North America. European and Oceanic events do occur, but are often operated by third parties. In addition, prize pools in North America that are backed by Activision, such as that of the recent MLG Anaheim tournament last weekend, are much more rich European prize pools. However, Puryear said he attended a Call of Duty event in France last month, when he witnessed excitement akin to sporting events around the world.

"We are definitely looking at all regions; Call of Duty is a worldwide title, and we're gonna go where the audience is," he said. "And we're gonna help support those audiences and those regions, to make sure that they're getting the support they need from the Call of Duty World League."

In many ways, Call of Duty esports is still a work in progress. The Call of Duty World League has had issues at times with network crashes, leading to postponement of matches and disgruntled players lashing out on Twitter. Another challenge is the Call of Duty release cycle. For every year since 2003, Call of Duty has put out a new version of the game around the holiday season. It brings a challenge that other esports games don't have, which is adaptation to something completely new. Luckily for Call of Duty, its multiple developers have begun to recognize what needs to stay consistent in order for esports success.

"Because we've got that cycle, Activision has stepped up, and it's a really a franchise initiative; so this isn't about one particular game. It's about letting the esports community know that Activision is active and behind esports," Puryear said. "So ensuring that some of the features we have, like CoDcaster, is in every single title moving forward; making sure that vendors are able to run LAN events. And really looking at the structure and stability that Call of Duty does bring, year after year, and letting the players and the community know that this is very important to us and that we're not going anywhere."

The World League has brought what feels like an upward swing to those involved in the Call of Duty community. For the first time, consistency is being utilized to properly promote the competitive side of the game, both to the player and to the viewer. It's still an uphill battle, especially considering other FPS games like Counter-Strike and Activision Blizzard's new game, Overwatch, are getting a lot of attention.

But for Puryear, he has no fear of competition, as long as his game and the team that makes it happen continue to provide to its player base.

"I think the first thing that's gonna separate us [from Overwatch, Counter-Strike and other esports] is that we're doing what's right for Call of Duty and the Call of Duty community," he said. "It's not just like a game over here or a game over there, so I think as the industry grows, it's good for everybody. ... For me, the fact that it can help grow the audience and the awareness is great, and now it's really up to the Call of Duty World League to make sure we are doing right by our community and our players to help grow where Call of Duty and where the Call of Duty World League can go."

ESPN reporter Tyler Erzberger contributed to this report.