Taking up almost a whole floor of the vast Encino Terrace Center, on a particularly soulless strip of the snaking Ventura Boulevard, Infinity Ward's office is… let's say lived in. A warren-like run of enclosed offices and small lounges cluster along a central corridor, with little natural light making its way in through the blinds. Apart from the life-size model of a spec ops soldier in the café, and the immense awards display cabinet in the reception, it's not obvious that this is where the biggest entertainment property in the world is developed.

And that's 'entertainment property' rather than 'game'. The last title in the series, Call of Duty: Black Ops, shifted over 25m copies, making an estimated $2bn for its publisher Activision. This figure dwarfs the box office takings of any movie or album release of last year – and through regular downloadable map packs, the millions are still rolling in. In a month's time, Modern Warfare 3 is likely to have broken a whole new bunch of records – pre-orders for the game are reportedly already comparable to those achieved by its predecessor.

This year, however, the game has an intimidating rival in the form of Battlefield 3, and EA is putting many millions into its marketing onslaught. Furthermore, there is a troubled history to recover from. Last March, Infinity Ward's co-founders Jason West and Vince Zampella left in a maelstrom of controversy and pending legal action, taking almost half the studio with them. The exodus meant that the remaining team members couldn't complete the project in time. So a plan was put forward. A new studio, Sledgehammer Games, originally tasked with producing a spin-off Call of Duty action adventure, would be brought in to help out. A dual-development – a weird, difficult and instantaneous relationship – was conjured. Suddenly, this was going to be a key year for the Call of Duty brand.



Infinity Ward 2.0

Walking in to the Infinity Ward HQ, there's no sense of any leftover drama. It's very quiet, everyone is getting on with last minute tweaks and corrections. Modern Warfare 3 executive producer Mark Rubin shows us in, and chats about bug-fixing and late nights at work. He's relaxed and affable as he explains the office layout. The team, it turns out, is divided into themed groups: one room will be single-player designers and gameplay engineers, another is multiplayer designers and engine coders, and another has animators, effects experts and related programmers.

"It's not, like, strike teams of designers, coders and artists – a lot of studios do that," says Rubin, referring perhaps to the agile development model that became trendy several years ago. "From what I understand talking to other developers, no one seems to work quite the way we do. But this system works for us. We have one producer, one production coordinator and that's it; we're not production driven, it's a very flat structure – everybody just knows what to do, and it gets done."

It's certainly a stark contrast to the set-up at Modern Warfare 3's other developer, who I visit the very next day. While Infinity Ward grew organically into its surroundings changing floors and room configurations as the headcount grew, Sledgehammer has inhabited its pristine open-floor space since founders Michael Condrey and Glen Schofield first started to hire staff in 2009.

For them, home is a high-tech chunk of office real estate in Foster City, regularly rated one of the best places to live in the US, and nestling on the periphery of Silicon Valley. Through the boardroom window there are rolling woodlands and a glittering lake, beside which the headquarters of Sony Computer Entertainment America is clearly visible. Nvidia, Facebook and Zynga are just down the road; Electronic Arts can also be seen from this office. "There's a great sandwich shop nearby that everyone goes to," says Condrey. "Sony goes, EA goes, our guys go… it's like (adopts a stern tone) 'Get your sandwich. Don't say a word to anyone while you're there!'"

The reception at Sledgehammer's lush office in Foster City, outside San Francisco.

This is a vast open office, with teams separated into spiralling pods of desks and low divides. According to Condrey, these are 'cross-functional' groups: "We get a designer, an engineer and a couple of artists – they come in as a team and we encourage them to own their level or area of the game." But there also seem to be a lot of impromptu meetings. Schofield and Condrey actually chose the interiors themselves with a clear idea of the working atmosphere they wanted to create. As Schofield explains, "What happens with an open environment is, you'll get three or four guys in one area who'll stand up and see something cool that someone else is working on, and instead of having to go from cubicle to cubicle telling everyone, sharing just happens naturally."

Inside Infinity

Back at Infinity Ward, Rubin takes us further into the complex. There's a games room complete with MAME cabinets and several foosball tables ("foosball is huge here," he confesses, pointing to a whiteboard that shows a recent in-house tournament named, 'Foosball Championship of the Universe Extreme 2011'). There's also a gym, which brilliantly provides the only access to the smoking balcony – "it's the walk of shame," says Rubin. Around the corner there's an office that's been converted into a mini-apartment for one of the artists. Apparently, he just wasn't leaving work that often – so now he sort of lives here.

The Infinity Ward cafe, complete with lifesize soldier dummy and Pac-Man wall decorations, here customised for Halloween.

Then we're into the cafeteria, which haphazardly doubles as the main meeting room. The walls are decorated with Pac-Man ghosts, the cupboards stuffed with boxes of chocolate bars. There is a sizeable drinks cabinet, which, among the gallons of hard liquor, boasts a huge bottle of Baileys – surely a concession to the studio's large contingent of British staff.

Hours here, like everywhere else in the games industry, are erratic and long. The basic shift is 10am to 7pm, though it's a while since anyone was doing that. Rubin says he usually arrives at 8.30am and, for the last month, has been regularly leaving at 4am. Certainly, there are staff around throughout the night – hence, the three massive refrigerator units filled with energy drinks. (On the plus side, the studio is visited weekly by a masseur, who sets up a table, lights some scented candles and provides a few moments respite from the crunch madness.)

One of the many Infinity Ward energy drink top-up points.

So one thing that's immediately obvious here: Infinity Ward and Sledgehammer have very different cultures. How did they work together? It turns out, they got into it almost straight away. "We started out sitting around a table down at Infinity ward, with probably five or six members from each team," recalls Schofield. "They had some 3x5 cards filled with ideas and we did as well – we came at it as fans, really."

It sounds tense, like two alley cats sizing each other up. "We were just feeling our way around each other," explains Schofield. "But we'd come to the same conclusions: that although the Modern Warfare story had started in the US, it now had to go global. We also agreed that we needed a really tight story – they understood MW2 was sketchy in places.

"From there, we started thinking, okay, if I'm commanding the Russian army, how would I invade these countries? And we didn't just say, 'well, let's go here, here and here'. We thought that London was the financial capital, Paris is a really iconic centre to attack, we looked at maps and plotted invasion routes… And we worked hard to ensure you always understand your objectives. We've also paired down the number of characters you play. It feels like a seamless story now.

Crucially, there's also an ending – of sorts. While Modern Warfare 2 closed on somewhat of an anti-climax, MW3 looks to be finishing off Russia's invasion of the Western world, overseen by elusive ultra-nationalist leader, Vladimir Makarov. "We needed to wrap up everything from the first two games," says Schofield. "It's not like we're ending a trilogy, but we're not leaving you with a cliffhanger – we're going to pay off on your investments in the characters and stories."

And on the subject of cliffhangers, come back tomorrow for part two of the feature...

21 October 2011 update: Here is part two