Bungie's lead writer Joseph Staten has said that when the developer was creating the character of Master Chief for Halo, "immersion" was key to what he would become.
In an interview with IG, Staten said it left out details from Chief's background to "increase immersion."
"The less players knew about the Chief, we believed, the more they would feel like the Chief," he said.
"When it came to the Halo novels and other products of the expanded universe, immersion wasn’t as important as deepening understanding."
He continued: "Immersion was the main goal here. Also keeping the Chief a man of few words reinforced what we wanted to be a tough-as-nails soldierly persona."
Staten also said that originally, Cortana was originally due to be just a simple guide in helping get Chief from A to B among some things. But as it turned out later on, Cortana would show a more human side to Chief.
"We needed a character who could consistently guide the player through the game, and an onboard A.I. was something that could always credibly accompany the player (i.e., another soldier might get lost, wounded etc)," Staten said.
"Over time, Cortana became a fully realized character—a friend and companion to the Chief, not to mention the only person to poke revealing holes in his tough-guy exterior.
"Through his interactions with Cortana, the Chief revealed his humanity (e.g., players learned the Chief had a sense of humor when he banged his helmet to stop Cortana from talking). And it was for these reasons that we focused so much on the Chief-Cortana relationship."
Bungie left behind the Halo universe last September with the release of Reach to work on its next big universe, which will be published by Activision under a ten-year deal.