- "A hero is more than a person, a hero is a belief. A belief that, against impossible odds, the world can be saved—and that the world is still worth saving. Heroes inspire that belief in us. They renew our faith and give us that most precious of all gifts—hope. The world needs heroes. That's why, when a true hero arrives, the world will honor him."
- — Xbox.com introduction of "Believe".
Believe is a Microsoft marketing campaign for Halo 3 produced by New Deal Studios. It features the word "Believe" as a tagline, and appears to be honoring the legacy of John-117, citing him as a hero of the United Nations Space Command whose brave actions inspired other servicemen during the Human-Covenant war.
It includes handouts, live-action TV commercials, magazine page advertisements, and Xbox live marketplace ads:
- Believe (Magazine) - An advertisement in the September 2007 issues of EGM (Electronic Gaming Monthly), OXM (Official Xbox Magazine), and other magazines around that month.
- Believe (Event) - A pamphlet distributed at the Project Revolution musical festival, featuring in-universe musical presentation of the UNSC Symphony Orchestra.
- Diorama - An interactive flash movie, a part of the Believe campaign for Halo 3. It is a fly through of the John-117 Monument, and could be viewed at the Halo 3 website. It has since disappeared along with most Believe content hosted on the website in the wake of the Halo: Reach prerelease redesign. Non-interactive walkthroughs are still available on peripheral websites such as YouTube.
- Museum - A live-action TV commercial featuring Retired Major Pawel Czernek, a UNSC veteran that fought in the Battle of New Mombasa alongside SPARTAN-117, reminiscing of his memories of the inspiring hero.
- Hunted - A live-action TV commercial.
- Enemy Weapon - A live-action TV commercial.
- Gravesite - A live-action TV commercial that explores the battleground and talks of Spartan 117's "death".
- Believe: The John 117 Monument - A live-action online video, describing the in-universe construction of the memorial diorama.
- The creators of the campaign were not informed of the story of Halo 3, leading to multiple inconsistencies with the story depicted in Believe, and the game's story. Due to this, no aspect of the marketing campaign can be considered canon.
- Because the events that were depicted in the interviews (the Second Battle of Mombasa and the capture and death of John-117) conflict with events as they transpired in Halo 3, the interviews may alternatively be a massive cover-up operation performed by ONI Section Two to cover up the truth about the Forerunners, the Halo Array, and the Flood.
- There was also an in-universe look at the creation of the Believe models.
- On Xbox.com, there is a collection of photographs from war photographer Jake Courage titled "Shooting a Hero".
- Stan Winston Studio was responsible for the diorama featured in the Halo 3 Believe ads.
- The melody that was used in the Believe commercials was created by Polish pianist Frédéric Chopin and is called "Preludes #15, Raindrop". Incidentally the Xbox 360 games Eternal Sonata is based on Chopin's death and Saints Row also contains "Raindrop".
- At the Halo 3: ODST map Mombasa Streets, there are several graffiti where you can read BELIEVE, maybe being a reference to the marketing campaign for Halo 3 of the same name.
- A new trailer released for the game Serious Sam HD entitled "Seriously Believe" is an obvious tribute or parody to the Believe campaign, utilizing a selection of frozen in-game views in place of the models, a similar track, and a black screen at the end with the words "Seriously Believe" appearing, very similar to the original "Believe" trailer.
- The "Believe" ad was named one of the best television ads of the decade by AdWeek.
- The "Believe" ads were the first times that the Human-Covenant war was given such a grim outlook outside of the comics and novels. This continued on to the Halo 3: ODST and Halo: Reach ads. Specifically, We Are ODST, and Deliver Hope.