First come the historians and then, increasingly, come the game designers: the second waves to break on the shorelines of our recent history. Just so long as that history's violent, obviously. Just so long as it has options for cover systems and alternate fire modes.
Treyarch's reached the 1960s. Actually, it's reached the Cold War in general, with a plotline that spans decades as you witness the birth and evolution of the Special Forces through a series of deniable operations filled with secret agendas and "unconventional weaponry".
At this week's Activision press event, the developer kicks off its presentation by showing a full cut of the teaser trailer - a trailer that suggests someone's seen Jacob's Ladder, as sun-bleached jungle shootouts are intercut with wobbly footage of something that looks like a military hospital viewed through a metric ton of Vaseline.
Betrayal is in, according to the voiceover, as are voiceovers, as this will be the first COD where the player character has dialogue. It's too early to say whether CIA LCD experiments are in (although a Treyarch take on Touch Fuzzy Get Dizzy would be wild) but during the extremely loud playthrough that follows, the developers demonstrate a single-player game with enough moment-to-moment variety to suggest it would be unwise to rule anything out.
With Infinity Ward's door swinging wide, Treyarch seems to be enjoying its time in the limelight: new level names are introduced with the gravitas of The Eagles announcing that the next song is Hotel California, while other members of the gaming press report that developer fist-bumpage was witnessed backstage.
This being a videogame as well as a full-blown cultural event, then, it's kind of pleasing to see that the first proper reveal of Black Ops involves an ice level and a fire level. Let's look at the ice first.
It's 1968 - not really, or I'd have quite a lot of bets to put on, and difficulty plugging my laptop in anywhere - and an American Special Forces division is deep behind enemy lines in the wilds of Russia. Snow falls, mountain ridges sparkle in the frosty sunlight: this is the Cold War at its most authentically chilly.
The level starts several miles above all that, however, as you find yourself stuck behind a shiny faceplate as a crewmember on an SR71 high-altitude reconnaissance craft.
Treyarch cuts the sequence down to get to the shooting, so it's hard to get a sense of how it plays, but it appears to be a neat inversion of one of the original Modern Warfare's most inspired moments, as you stare down into a grainy screen and place waypoints to lead a ground team past enemy patrols far, far below you.
In reality, the sequence is there to remind you how iconic this period is: the space race, sleek black spy planes, computers the size of refrigerators. If Treyarch takes care over the details - and it certainly seems to be doing just that - this could be every bit as enjoyable to buzz through as the dodgy War on Terror chic of Modern Warfare.
Before you have time to say, "Ooh, Bakelite!" we're out of the heavens and back on the ground, however, playing as a member of the insertion team as they work their way down a mountainside towards a military installation buried in a freezing canyon of rock.
There are guards to avoid, twisty paths to navigate, and - lovely - a scoped crossbow to wield. The curvy lens does a great job of picking out distant soldiers, and there's always something a bit special about shooting someone with a crossbow, isn't there?