It seems unlikely now, but for years, the Call of Duty games were mere solid performers, beloved by fans of first-person shooters but nowhere near the general public's pop-culture radar.
But 2007's Modern Warfare propelled the franchise into the stratosphere in sales terms, producing revenues so titanic that the launch of every subsequent CoD game has been a bona fide pop-culture zeitgeist moment. So, how did Modern Warfare get so big?
The first stirrings
To get to the roots of the Modern Warfare games, you have to go back to a surprising place: 2002's Medal of Honor: Allied Assault, published by Activision's deadly rival Electronic Arts. After that much-loved WWII fps came out, developer 2015 had an almighty falling out with EA, and 22 key members of the team left to form a new developer called Infinity Ward.
Activision schmoozed the three co-founders - Vince Zampella, Jason West and Grant Collier - and bought 30 per cent of the fledgling company. Thus Call of Duty was born: the first thusly named game arriving for the PC in 2003. Call of Duty 2 - like its predecessor set in WWII - came along in 2005, with Infinity Ward justly proud that it was one of the few games ready for the launch of Microsoft's Xbox 360 console.
World War II is over
Feeling that, over the years, they had done World War II to death, the Infinity Ward crew, with Activision's solid backing, took what now looks like a genius decision: to set its next first-person shooter in an up-to-date setting. It would be called Call of Duty: Modern Warfare.
Activision, meanwhile, swiftly realised that it had a major franchise on its hands, and commissioned another developer Treyarch, to make a third Call of Duty game, which would go on sale in 2006, while Infinity Ward took two years to perfect Modern Warfare.
So, in November 2007, the Modern Warfare sub-franchise was unleashed on an unsuspecting world, and it wouldn't be too much of a stretch to assert that it changed the videogames industry forever, permanently erasing the previously widespread view that games were a mere adjunct to pop-culture, rather than one of its central pillars.
Call of Duty: Modern Warfare was a mega-hit - during its first 18 months in the shops, it notched 13 million sales. Just as lavish was the critical acclaim it received.
Modern Warfare's single-player was the point of entry for most people who bought it, and it became instantly apparent that it considerably raised the bar compared to previous fps games - while not the longest, it was chock-full of spectacular set-pieces and Hollywood-style cliffhangers.
The game's plot centred on Russian ultra-nationalist leader Imran Zakhaev, who had funded a military coup in an (unnamed) Middle eastern country to take the heat off his activities closer to home. This device allowed gamers to play as six different military characters, including the enduring Soap MacTavish of the SAS and the US Marine Sergeant Paul Jackson.
The action concentrated mainly on Russia and the Middle East, and was impressively varied for a first-person shooter - for example, at one point, you took on the role of a thermal-imaging operative on an AC-130 gunship above a battle-zone.
But Modern Warfare's biggest legacy, undoubtedly, lay in its multiplayer component. It's team-based and deathmatch modes really hit a chord, and its use of XP to rank you up according to your actions led to a massive constituency of gamers becoming completely hooked.
It also introduced the concept of Killstreaks, which meant that if you took out a string of enemies without being killed yourself, you could earn goodies like air-strikes.
Modern warfare came out at just the right time, since Microsoft's Xbox Live online service had just reached maturity, and finally, broadband was pretty much available to all UK consumers. Modern Warfare swiftly became responsible for more multiplayer action than any console game before it, and single-handedly created a whole generation of online console gamers.