Microsoft has known how important Halo 3 will be to their success this generation since before they even announced the Xbox 360. Halo 2 sold $125 million on the first day, but then the original Xbox was just struggling for recognition in the wake of the PS2 juggernaut. Now the 360 holds a tenuous lead in installed base and isn’t selling the way Microsoft may have hoped. If it’s possible Halo 3 may have become even more important to Microsoft’s strategy than they originally hoped. Fortunately, they’ve been planning ahead.

In an article released today on Brand Week, the calculated ten-month marketing efforts behind Bungie‘s trilogy finale is dissected starting from the Starry Nights TV spot launched last November through the public beta this spring/early summer. They talk about the Project Iris viral campaign and the efforts they’ve gone to secure strategic branding partners. This has included the Mountain Dew Game Fuel limited edition soft drink that comes plastered with Halo 3 imagery plus a total of $5 million from Pontiac to help push the launch of the game on September 25.

And they aren’t done yet. Microsoft will begin the full blitz with the new Believe campaign that will lead up to the launch taking place at midnight in over 10,000 stores to give Halo fans a chance to grab the game as soon as possible. It’s an interesting read about the science behind building a monster.