In all Metal Gear games, there are at least two enemy statuses: Normal mode and Alert mode.
- Normal mode - Situation normal, when the enemy has not detected the player. In this mode, enemies generally patrol along a certain route.
- Alert mode - In Alert mode, the enemy will converge on the player and attack. The mode is accompanied by an exclamation point appearing above the alerted enemy, a change in background music (BGM), and the jamming of any radar equipment. In some cases, the alert mode will also have enemy soldiers requesting backup to deal with the intruder, which may or may not be granted. Alert mode remains in effect until the enemy either loses sight of the player or is defeated.
In the original Metal Gear, there are two enemy statuses: Normal mode and Alert mode.
|Normal mode||Situation normal, when the enemy has not detected the player. Enemy soldiers will walk their rounds (patrol routes), checking to make sure nothing is out of the ordinary.|
|Alert mode||When the enemy detects the player, they go into Alert mode.
Metal Gear 2: Solid Snake
In Metal Gear 2: Solid Snake, there are four enemy statuses: Normal mode, Noise mode, Alert mode, and Evasion mode. Metal Gear 2 introduces radar jamming as a feature of Alert mode, and the countdown timer, which determines when the next mode occurs, depending on the player's actions. According to the game plan by Hideo Kojima, the increased amount of enemy statuses compared to the prior game was in an effort to make the infiltration simulation even more realistic.
|Normal mode (Level 1)||This is the normal mode, when the player has avoided detection by enemy soldiers and surveillance cameras. Enemy soldiers will walk their rounds (patrol routes), checking to make sure nothing is out of the ordinary. Various sensors will also be operating, watching for intruders. The radar will be functioning, so read the enemy movements within the radar and proceed in a way that will avoid detection.|
|Noise mode (Level 1)||If the player makes sounds in Normal mode (punching or footsteps), enemy soldiers will stop patrolling and enter Noise mode to investigate the source of the sound. Once they confirm that nothing is out of the ordinary, they will return to their patrol routes and go back to Normal mode.|
|Alert mode (Level 3)||The player will enter into Alert mode if the player is detected by guards or sensors. The BGM will change and the enemy will attack the player, calling for reinforcements. The radar will display the word “Alert” and show how much LIFE the player has left.|
|Evasion mode (Level 2)||If the player is in Alert mode and escapes to a screen where there are no enemies, the player will enter Evasion mode. At this time, the player will have two enemy soldiers following the player in pursuit. They will search for the player in this screen for a set period of time. The radar will display the word “Evasion” and show how much time is left before they give up their pursuit.|
Metal Gear Solid and Ghost Babel
|Infiltration mode||The standard mode when enemy soldiers or surveillance cameras have not discovered Snake. In this mode, enemies generally patrol along a certain route.|
|Noise mode||When the enemy soldiers hear a noise in Infiltration mode, they leave their patrol route and investigate in the direction of the noise. In this mode, the enemy’s field of vision is displayed on the radar as a red cone. If the enemy soldiers search the area where the noise was made and find nothing unusual, they return to their normal patrol routes. The player can intentionally make a noise to lure the enemy soldiers in a particular direction. When the player kills enemies, they might drop an item.|
|Alert mode||When an enemy soldier or a surveillance camera discovers Snake, the game enters Alert mode. In Alert mode, the enemy soldiers call in reinforcements and attack Snake.
If the soldiers lose sight of Snake, the game enters Evasion mode. In this mode, because the enemies already know that Snake is nearby, they don’t enter Noise mode even if a noise is made.
|Evasion mode||If the enemy soldiers rediscover Snake in Evasion mode, the game reenters Alert mode. However, if the player stays out of sight of the enemy until the counter reaches zero, the game once again enters Infiltration mode, and the enemies quickly return to their patrol routes. In Evasion mode, just as in Infiltration mode, the player can make noise to lure the enemy in a particular direction.|
Sons of Liberty, The Twin Snakes, and Metal Gear Acid
Metal Gear Solid 2: Sons of Liberty introduces the Caution mode, which occurs after Evasion mode. The player can also prevent Alert mode after being spotted by preventing the enemy from contacting their HQ by radio. This system is carried over to the remake Metal Gear Solid: The Twin Snakes and the Metal Gear Acid games.
|Normal mode||This is the default state, when the player has not been discovered by enemy soldiers or surveillance cameras. While in Normal mode, enemy soldiers will follow a set patrol route. When a soldier in Normal mode hears a noise or spots something suspicious, such as footprints or bloodstains, he will leave his patrol route and search the surrounding area. If he finds nothing out of the ordinary in the area, the soldier will return to his patrol route.|
|Alert mode||This is the state in which the player has been discovered by enemy soldiers or surveillance cameras. In Alert mode, enemy soldiers call for backup and attack. The player can get out of Alert mode only by eluding the enemy soldiers or defeating a certain number of them.|
|Evasion mode||In this mode, enemy soldiers will search the vicinity after losing sight of the player. When the player eludes the enemy soldiers by hiding under a table or in a locker, the enemy soldiers may perform a “Clearing.” This means that the soldiers will conduct a sweep of the area and “clean out” any spots where they suspect the player may be hiding. When the clearing is complete, or after searching for a certain period of time, the enemy soldiers will switch to Caution mode.|
|Caution mode||In Caution mode, enemy soldiers will be more vigilant than usual in their patrols. In certain cases, extra soldiers may be added to the patrols as well.|
Snake Eater to Peace Walker
Metal Gear Solid 3: Snake Eater maintains the enemy statuses from its predecessor, but removes the ability for the player to avoid Alert mode after being spotted. This system carries over to Metal Gear Solid: Portable Ops, Metal Gear Solid 4: Guns of the Patriots, and Metal Gear Solid: Peace Walker.
|Normal mode||Occurs when Snake has not been spotted by the enemy. In Normal Mode, enemy soldiers will usually patrol an assigned area (patrol route) and check for any disturbances. Some soldiers will stand in a fixed position and keep a lookout. Enemy soldiers have senses of sight and hearing. If they hear a noise or see something suspicious, they will leave their patrol route and investigate the area. If nothing unusual is found, the soldiers will return to their assigned patrol route. Enemy soldiers have a number of different statuses, each represented by a different mark above the soldier’s head.|
|Alert mode||Occurs when the enemy spots Snake. In Alert Mode, enemy soldiers will call their comrades on the radio and attack. To get out of Alert Mode, Snake must either escape from the enemy or defeat a certain number of them. Once Snake has escaped from the enemy’s line of sight and the number in the Mode Gauge reaches zero, the game will switch to Evasion Mode.|
|Evasion mode||Occurs when the enemy has lost sight of Snake and is actively searching the area for him. In this mode, Snake may be found while hiding in trees, in lockers, or under tables. Once the number in the Mode Gauge reaches zero, the game will switch to Caution Mode.|
|Caution mode||In Caution Mode, enemy soldiers are more vigilant than usual in their patrols. In some locations, the number of soldiers on patrol may be increased. Once the number in the Mode Gauge reaches zero, the game will switch back to Normal Mode.|
Metal Gear Solid V
|Normal mode||Normal mode is when the enemies don't know you are in the base and when nothing suspicious happens they patrol a certain area without being that cautious. Also you don't have to be very cautious as well.|
|Alert mode||Alert mode is when the enemies still don't know you are in the base, but something suspicious has happened and this causes the enemies to be more cautious. Normally soldiers will going around areas and checking if there are any hostiles. Also you will have to be more cautious as well. If the enemies don't find anything, you will go back to normal mode.|
|Combat mode||Combat mode occurs when the enemy discovers you and starts attacking. If the player has Reflex Mode enabled, combat mode can be avoided by successfully neutralizing any alerted enemy soldiers within a short time period, before they can alert others.|
|Commencing search mode||When you're in combat status and you have escaped. Enemies will start to search for you. You get the chance to have Reflex Mode. If you kill or neutralise the enemy (or enemies) before the reflex mode ends you will prevent them from alerting the other enemies and you will still stay in commencing search mode. Commencing search mode is when the enemies know you're in the base, but they've lost contact with you. If you get detected, you will go back into combat mode. If you manage to hide away from the enemies for a certain amount of time, you will enter alert mode and then gradually enter into normal mode.|
In the first encounter with Metal Gear Sahelanthropus, the mech is shown to have similar modes to Alert Mode, Commencing Search Mode, and Combat Mode, which are indicated by the visor light colors (blue, yellow, and red, respectively).