M18 Claymore anti-personnel mine

"The M18A1 Claymore is a new type of anti-personnel directional mine developed in the US after the Korean War."

- Sigint

The M18A1 Claymore Anti-Personnel Mine was developed in the U.S. after the Korean War. The curved casing is packed with a pound and a half of powerful explosives. The side facing the enemy is lined with 700 steel ball bearings, so when the mine explodes, the ball bearings simultaneously burst out of the casing. The mine is triggered by an electric detonator. When the mine is planted, it reacts to anything that comes close and automatically explodes.

M18A1 Claymore anti-personnel mines are used for ambushing an enemy without exposing the explosive itself to the enemy. Because they can be difficult to detect, sensors have to be used to avoid them. Crawling over them allows Snake to pick them up safely.

The Claymore mines in Metal Gear Solid and Metal Gear Solid 2 were enhanced with built-in Stealth Camouflage, and utilizes a short ranged 90º laser sight to trigger the detonation. During the Shadow Moses Incident, three Space Seal members brought in two containers, one of which containing M18A1 in addition to other explosives, to deliver to Liquid Snake. This, along with the fact that the path between the Tank hangar and the Warhead Storage Building had Claymore mines littered about, implies that the Sons of Big Boss used these weapons. In Metal Gear Solid 4 they work the same way, but are not Stealth-equipped.

The Claymore mines ended up having a slightly major role during the San Hieronymo Takeover, as a mission during the events of the conflict had Gene's army secretly placing Claymore Mines throughout the Hospital Area, which would have caused a devastating hazard to the hospital staff (who were not informed of the incident), especially a nurse on a late shift, had Snake's Spy Unit not informed the resistance and disarmed all of them.

Counter measures

 * Thermal Goggles make Claymore Mines visible.
 * Mine Detectors are obviously useful for locating them. Early versions of this sensor would vibrate as you got closer to a mine. Later versions would display the location of mines on the Soliton Radar. (The first in-game appearance of the mine detector, in Metal Gear, actually revealed the mines.)
 * Unlike the previous games, in Metal Gear Solid 3 and 4 you can spot a Claymore mine with your naked eye. They can be tough to spot, though.
 * In MGS4, you can send the Metal Gear MK. II/III to scout ahead for mines. These can then be disarmed with the ▲(triangle) button.