Do smoke grenades do anything in the campaign?

Question

Do smoke grenades do anything in any of the Call of Duty campaigns? Will it affect the movement of AI, shooting, cones of vision, alter their behavior, etc.?

Answer 1

According to a Call of Duty wiki, smoke grenades can serve a purpose in single-player, and it varies per game:

Call of Duty 4: Modern Warfare

The only time smoke grenades are available instead of flash-bang grenades is "All In", which are used for approaching a BMP in order to plant a C4 on it, and "Heat", where they can be used for hiding the player's advance.

Call of Duty 4: Modern Warfare (Nintendo DS)

Enemies caught in the radius of the smoke will be covering their mouth and nose with one hand and attempting to wave the smoke away with the other hand. If the player is in the radius of the smoke, enemies will not notice the player, if they do, their shots will usually miss the player. This smoke grenade produces very little smoke in some missions (like "Missile Away") but in others it produces a lot of smoke.

Call of Duty: World at War

The smoke grenade is basically the same as in Call of Duty 4: Modern Warfare but with minor differences. In single player, it is the Marine default secondary grenade. These can be very helpful on Veteran difficulty if a player is stuck while advancing through a level.

(So we can assume they hinder the visibility of the enemy)

Call of Duty: Black Ops II

Hudson throws smoke grenades in "Pyrrhic Victory" during their escape. They are also the player's recommended tactical grenade in "Time and Fate".

As above, regarding "the player's recommended tactical grenade" we can assume it serves some useful function.