One Man Army

One Man Army, sometimes known as "OMA", is a Tier 1 perk available in the multiplayer of Call of Duty: Modern Warfare 2. It allows the user to switch classes without needing to respawn, unlocked at level 45. However, as downside, it removes the user's secondary weapon.

There is a five second waiting period during which time the player can only move, crouch, jump and prone. When the player switches from their primary weapon to the backpack, it brings up the class menu. From there the player can pick the class desired to switch to. Users can switch to the same class repeatedly, or through several different classes with One Man Army.

One Man Army Pro is unlocked after a player has received 120 kills while using the One Man Army perk. One Man Army Pro reduces the time required to perform the class change to three seconds.

Tactics
Although One Man Army is commonly used for constantly resupplying Grenade Launcher grenades, it also can be used in a variety of ways.

However, One Man Army was intended for more tactical gameplay. For example, a player using the perk could have several classes, all with One Man Army equipped, for a rapid change of playstyle during certain events in the game. One class could feature Stopping Power, enabling quicker kills with weapons, while one could use Hardline. Using Hardline in combination with a Predator Missile could help with attaining Harriers or the Attack Helicopter, as it only would require one kill with the missile, which is almost guaranteed. Another OMA class could also feature Cold-Blooded, to avoid enemy air support. Danger Close could also be used in this respect, while powerful killstreaks such as the AC-130 are being deployed.

Using C4s with One Man Army, to constantly defend or trap an objective is also a viable tactic. This can be used in conjunction with claymores, repeatedly switching out to get the maximum 2 claymores and C4 out at a time. This tactic can be especially effective in Hardcore, where enemies are unlikely to know where the C4 was thrown from, as well as the decreased health which means the C4 is more likely to kill. This can be especially useful in Capture the Flag, Domination and to an extent, Headquarters Pro.

One Man Army can also be used as an alternative to Sleight of Hand or Scavenger with certain LMGs. The RPD and MG4 have longer reload times than switching with One Man Army takes, and using this also resupplies equipment and ammo.

With coordination, a team using OMA with Claymores, then perhaps switching to a Scavenger class, can start off a game fortifying control zones of maps, being able to plant two claymores each within a short period of time.

Using a sniper rifle with OMA is risky unless in an easy to defend area, as having a secondary is vital for close quarters encounters while using a sniper. However, using such a rifle at the start of games such as the spawn on Highrise can help getting quick kills from the spawn, then switching to a more suitable class.

Tips

 * An easy way to get One Man Army Pro without having to use it is to simply switch to the desired class at the beginning of a life. Any kills performed with the new class will still count as an OMA kill. Placing a claymore before switching classes can help.
 * Entering prestige mode helps getting the most out of One Man Army, as the player will have more custom class slots.
 * A C4 can be used while switching classes, as the double-tap method of detonating the explosive is still available to use while switching.
 * It can be used to place a claymore then to place a C4 on it to make the claymore set off the C4, making it much more lethal.

Trivia

 * A One Man Army pack is visible during the mission "S.S.D.D.", near the first intel item and at the "door" of The PitOMA_bag_campaign_ssdd.jpg.
 * When the player switches between classes with One Man Army, their character model changes with it. For example, while sniping the player wears their ghillie suit, and after switching to a different weapon class, they will have a different appearance.
 * When a player is changing their kit, their character's hand covers the words "No Scope." This is most noticeable in the mission S.S.D.D.
 * OMA cannot be used to repair a riot shield. If using One Man Army with a riot shield as the player's primary and they use the pack to reset it, the shield will still have any cracks it had beforehand.
 * In multiplayer when a player is switching classes using OMA, the OMA pack disappears.
 * The One Man Army pack makes players wearing it more easily noticeable, as it protrudes very visibly from their back.
 * In Terminal (Special Ops level), if the player kills one of the Russian police with a Riot Shield he/she will see a green bag that looks like the One Man Army perk.
 * The sounds One Man Army makes while changing kits are similar to the suiting-up sounds in the beginning of "No Russian".
 * If a player is changing classes via One Man Army when host migration occurs, after the host migration, the player will just be holding the backpack. They can perform most normal actions with it, i.e. jumping, running, climbing, but cannot shoot, change classes (with the backpack), or switch weapons. However, if player picks up another weapon from the ground, the backpack will disappear. The picked up weapon will be the only weapon the player is holding, no original primary weapon and no secondary. In addition to this, the pack can be swung using the knife attack and do the same damage as a knife. The visual from an observer is of the pack holder hitting the opponent in a manner similar to swinging a pillow.
 * If using One Man Army and Last Stand after choosing a class it will continue to switch giving the gun of choice instead of pistol. However, the player will still die.
 * On the back of the One Man Army bag, in white letters it says "OMA", obviously standing for One Man Army.
 * This perk will not be returning in Call of Duty: Black Ops due to complaints from many players.
 * In the Spanish version of the game the perk is called "Camaleón" which in English means chameleon.
 * One Man Army is an award in the DS version of World at War for killing 1500 enemies.