Bots

Bots (known as a short term for robots) are A.I. controlled players that appear in Call of Duty: Black Ops, Call of Duty: Black Ops II, Call of Duty: Ghosts, Call of Duty: Advanced Warfare and Call of Duty: Black Ops III. Bots appear in offline multiplayer or combat training online as well as online local or system link lobby. Bots have four different difficulties (on Ghosts and Advanced Warfare there is five) those difficulties are Recruit, Regular, Hardened and Veteran, plus the "Mixed" difficulty in Ghosts and Advanced Warfare. Bots are seen only on local or system link lobbies as well as online Combat Training.

Call of Duty: Black Ops
In Call of Duty: Black Ops, Bots first appeared in this game in a combat training lobby. They can be activated by going to the edit game options section and changing the number of friendly and hostile bots. In Recruit and Regular difficulty, Bots use weak tactics and never check what's behind them. In Hardened and Veteran mode, bots use all of their tactics and focus and checks who is behind them, and they can usually hear enemies' steps. Bots can use all kind of weapons and equipments. The bots have their clan tag set to [3arc], which is the clan tag used exclusively by Treyarch members.

The player can play the following game modes with bots:
 * Team Deathmatch
 * Hardcore Team Deathmatch (online only)
 * Free for all
 * Hardcore Free for all (online only)

Call of Duty: Black Ops II
In Call of Duty: Black Ops II the bots are back and are smarter than they were on Black Ops. In Black Ops II bots are smarter and are now able to capture objectives. They not only appear in offline multiplayer, they also appear online on Combat Training on both Boot camp and Objective. If a player leaves a combat training lobby early, a bot will replace the player's role. When a new player is joining a session, one of the AI players will leave and give room to the new player. They also have their clan set to [3arc], just like they did in Black Ops.

The player can play the following game modes with bots: There are a handful of gamemodes online where the player can play with bots:
 * Team Deathmatch
 * Kill Confirmed
 * Domination
 * Demolition
 * Free for all
 * Capture the Flag
 * Headquarters
 * Hardpoint
 * Bootcamp: A game where teams of mixed humans and bots face each other on Team Deathmatch.  Bootcamp is available to players who are below Level 10; once they reach level 10 or higher they can no longer access this game mode. Players earn full XP from playing it.
 * Objective: A game of when any player of any level can play a different gamemode besides team deathmatch, all game modes (expect for search and destory and party games) can be randomly picked to play. Players will earn half XP.

Call of Duty: Ghosts
In Call of Duty: Ghosts bots are now much smarter and they will play like a normal human player would in a Call of Duty game, using different tactics similar to actual players. They have the same four difficulties the bots have in Black Ops II but a new one called Mixed that randomly picks each bot a different difficulty. The player can now choose a bot difficulty for each bot team. The bots can also be noted to have a level based on their difficulty, i.e. a Recruit bot will be about level 1 - 10 and a Veteran one will be level 60.

Bots are supported in all game modes.

Call of Duty: Advanced Warfare
Bots also appear in Call of Duty: Advanced Warfare. They can appear with Supply Drop weapons variants, can use all perks and equipments and scorestreaks. They can also use exo movements. Just like they were in Ghosts, they are supported in all game modes. The Mixed difficulty also returns. However, in Advanced Warfare, bots are now smart enough to pick up weapons off the ground, such as if they are only armed with a Combat Knife.

Call of Duty: Black Ops III
Bots return in Call of Duty: Black Ops III. The bots are slightly smarter then they were in Black Ops and Black Ops II. In Black Ops III, bots are now supported in all game modes, unlike Black Ops II, where they weren't able to play in Party Games or Search and Destroy.

Bots have four difficulties: Recruit, Regular, Hardened, and Veteran. The difficulties seems to control each bot's aggressiveness, weapons and speed. For example, in Recruit, the bots are not aggressive, and their weapons are usually weak and don't cause a lot of damage and they won't run for a long period. On Veteran, the bots are extremely aggressive, and the weapons Veteran bots choose are more likely to have high damage and fire rate and they will run, and boost jump a lot. For unknown reasons, bots are programmed not to wall run even if they are chasing their target. The bots can still boost jump, use specialists abilities, and swim.

In the Xbox One, PlayStation 4 and PC versions of Black Ops III, the bots use the 3arc clan tag. In the Xbox 360 and PlayStation 3 versions of Black Ops III, the bots use the ATVI clan tag.

Trivia

 * Bots can be kicked due to friendly fire.
 * Bots will throw any lethal or tactical at the enemy if they are in cover or next to them.
 * Sometimes, in Call of Duty: Advanced Warfare, bots will "see" the player through walls and will fire at the player, sometimes securing the kill.
 * Hardened or Veteran Bots that are shot by their teammate will attack the ally who shot them.
 * Even on Recruit the bots will always aim for the head when an enemy is in range and sight.
 * They are also able to revieve a player in second chance, but only when they have the perk themselves.