With all the discussion about safety mechanisms in the previous few posts, it is now time to discuss the subject of carry conditions, i.e. how to carry a firearm in various conditions of readiness. The various carry conditions were defined by the legendary Marine Lieutenant Colonel John Dean ("Jeff") Cooper, who did much to teach the modern techniques of handgun shooting.
Before discussing the various carry conditions, it must be noted that Lt. Col. Cooper was a big fan of the Colt M1911 and its variants. So when he defined his carrying conditions, it was with such a pistol in mind (i.e.) a semi-automatic with an exposed hammer. Therefore, some of the carry conditions may not apply to other firearm types. With that said, let us discuss the various carry conditions (from safest to readiest) and where they are used:
Condition 4: This is the safest of the carry conditions. In this condition, the firearm is completely unloaded. There is no cartridge in the chamber and the magazine is removed from the firearm. The hammer is lowered as well. Also, all safety devices on the firearm are turned on. In some firearm types (e.g. shotguns, rifles), the firearm may be partially disassembled as well (e.g. barrel separated from receiver), so that it will fit in a bag or case. In this condition, it will take a while to get the firearm ready to fire, because the user needs to load a magazine, insert it into the firearm, feed the first round into the firing chamber by operating the slide (which also cocks the hammer in pistols), disable all safety devices and then pull the trigger. Many people put their firearms in this condition, when they intend to store them for a long while in a gun vault (say, at the end of hunting season.)
Condition 3: In this condition, there is a loaded magazine inserted into the weapon, but there is no round in the chamber. The hammer is also down and all safety devices on the firearm are enabled. In this condition, the user needs to pull back the slide to feed the first round into the pistol's chamber (which also cocks it) and then disable all safety devices and then pull the trigger to fire. In case of a shotgun or a bolt action rifle, the user pulls on the lever to load the first round and cock the weapon. This is the condition that many people preferred to carry single or double action revolvers in, back in the day when there were no other safety devices on them. The revolver is loaded in all chambers, except for the one that is rotated to be directly under the hammer. Any unintentional impact on the hammer will not do any harm because the chamber under the hammer is empty. When the user intends to use the revolver, they pull the hammer back first to cock it, which automatically rotates the cylinder as well and now the next chamber with a cartridge comes under the hammer, ready to be discharged. The early Israeli weapons training in the 1940-60s also emphasized carrying firearms with no round in the chamber and hence this condition is also called the "Israeli Carry" method. The reason the Israelis taught this method is because when the new state of Israel was founded, most of its weaponry was old, second-hand goods. This meant that quite a few of their firearms had worn or malfunctioning safety devices and therefore new soldiers were taught to use condition 3 carry in order to prevent accidents. Since then, Israel has started manufacturing her own firearms and also can purchase quality firearms from other countries now, hence they no longer teach this method to new soldiers. Other people who carry in condition 3 are usually owners of older revolvers with no firing pin safety, or those who own a firearm with no external hammer (such as a Glock, Springfield XD, many pocket pistols from Browning, FN, Colt, Astra etc.) and wish to be extra safe.
Condition 2: In this condition, there is a loaded magazine inserted into the firearm and one round is loaded in the chamber already. However, the hammer is decocked. Therefore, to fire a weapon in this condition, one needs to pull the hammer back to cock it and then pull the trigger. This condition only applies to firearms with external hammers. Therefore it is not possible to carry a firearm with an internal striker (such as a Glock or a Springfield Armory XD pistol) in this condition. Also, it is recommended that the firearm have some kind of firing pin safety enabled, if carrying in this condition and preferably a decocking lever to safely decock the weapon. A double action (DA) revolver or pistol may be carried in this condition because the first pull of the trigger is much heavier (because it cocks the hammer first before firing it). Subsequent shots on a DA pistol are much easier because each shot now automatically re-cocks the pistol as well. A single action revolver with no firing pin safety (or a pistol with no firing pin safety) should never be carried in condition 2.
Condition 1: In this condition, a loaded magazine is inserted into the firearm, there is a round in the chamber and the hammer is cocked. Only the safety device(s) is enabled. This is also called the "cocked-and-locked" condition. To fire a weapon in this condition, one merely disables the safety device and then pulls the trigger. On a pistol such as a M1911, the thumb safety is enabled and the user needs to merely flick it down with the thumb and pull the trigger. This is the condition recommended for concealed carry and also recommended for use by some militaries when soldiers are travelling through a potentially hazardous zone with no visible danger apparent.
Condition 0: This is the condition where the firearm is in its most ready state. A loaded magazine is inserted into the firearm, there is a round in the chamber, the hammer is cocked and all safety devices are disabled. The user only needs to aim and pull the trigger to discharge it. This is the condition that police and soldiers carry their weapons in, if they are in a danger area with known enemies in the vicinity.
Some people consider a loaded Glock or Springfield XD pistol with no separate external safety, to be in Condition 0.5 (i.e. between conditions 0 and 1). This is because the built in safeties are enabled, but they are all connected to the trigger and once the trigger is pulled, it automatically disables all the safeties as part of the action. How this mechanism works was explained earlier in our discussion about integrated trigger safeties.
Organizations that issue M1911 style pistols usually specify the condition it is to be carried in, as part of their training doctrine.
While the carry conditions were originally written for M1911 type pistols, they generally apply to other firearms as well. While military doctrines clearly define what carry condition should be used in what situation, the same is not true in the civilian sector. Therefore, one invariably sees many arguments about which condition is best on various internet boards :).