Let’s clear the air before we get down and dirty on how ready a particular pistol is ready to fire. The condition system (“Condition 0, Condition 1, Condition 2, Condition 3, Condition 4”) is directly related to United States military manuals on their issued firearms. This condition system is meant to describe the number of steps to take a firearm from unloaded to ready to fire.
If we were talking about the M-16A2 semiautomatic rifle, there are five listed conditions according to the Marine Corps manual on this firearm despite only needing four steps to go from unloaded to ready to fire. For the M9 (MCRP 3-OIB, page 28), there are also five listed conditions while only four apply.
This makes it extremely difficult to “get it straight” when discussing firearm conditions.
The original “firearm conditions” were listed out by a guy named John Dean (“Jeff”) Cooper and they were specifically for the Colt M1911A1. His issued Colt M1911A1 that he used to develop modern handgun techniques had five basic firearm conditions.