There is a five second waiting period during which time the player can only move, crouch, jump and prone. However, as a downside, it removes the user's secondary weapon. It allows the user to switch classes without needing to respawn.
One Man Army (sometimes abbreviated as ' OMA') is a Tier 1 perk available in the multiplayer of Call of Duty: Modern Warfare 2. One_man_army For the bag itself, see One Man Army Bag.