When completing an operation in MGS5 you receive a ranking and a codename, based on your performance. How is the code name determined? In previous MGS games, the codename was based off of specific (usually hidden) criteria you met during the mission. If the same system is used, what are the criteria? And do the codenames have any affect on the rest of the game?
Your codename is based not just on the mission you just did, but also the previous two missions before that.
Starting with the completion of mission 06, the game will give you a codename based on how you did the three previous missions. Prior to mission 06, the only codename you will receive is Chick (and possibly Chicken if you actually use the chicken hat, but I can't confirm that). The majority of the codenames are based on the method you used to neutralize enemies, although two (possibly three) codenames take priority if the conditions for them are met. Some (not all!) of the codenames you can get are as follows:
- Foxhound: Three consecutive "Perfect Stealth, No Kills" (never spotted by an enemy, no kills during the mission), overrides all other codenames
- Fox: You were not detected in the last three missions (or, if you were spotted and Reflex Mode was enabled, you neutralized the enemy during Reflex)
- Octopus: majority of enemy neutralizations was using nonlethal weapons (e.g. Wu pistol)
- Bear: majority of the enemy neutralizations was using CQC
A (brief) google indicates there's a different codename for each class of lethal weapon (handguns, shotguns, smgs, and so on) and also for using support (heli, carpet-bombs) and buddies to neutralize enemies.