Fire discipline is a system of communication in the military, primarily for directing artillery. By definition, fire discipline is the language of fire control. It consists of words, phrases, rules, and conventions which have specific meanings and which result in some definite action being taken with the guns. All ranks concerned in fire control must be thoroughly familiar with the language and the resulting actions. The aim of fire discipline is to ensure that in response to calls for fire (from a forward observer), the appropriate action is taken at the FPC (future planning cell), FSCC (fire support coordination center), FDC (fire direction center) and at the Guns/MRL, strictly in accordance with the intentions of the originator and with the minimum of delay.

An initial call for fire (to an artillery battery) consists of six elements:

In the United States military, artillery is usually brought into play when a forward observer sends a three-part "call for fire". While there are many "missions" available, the most common in a wartime scenario is the basic "adjust fire":

Fire missions are started with a warning stating the observer identification (call sign) and the type of mission to be fired: "M10, this is G35, adjust fire, over."

The next radio transmission will be from the artillery battery, mirroring what was sent: "G35, this is M10, adjust fire, out."

The forward observer then sends a six-digit Military Grid Reference System (MGRS) grid coordinate with a 100-metre grid square identifier: "Grid ES 923 945, over".

The forward observer will always get a reply mirroring what was originally sent: "Grid ES 923 945, out."

The last element is the description of the target, and optionally, method of engagement and method of fire and control: "Two BMPs and 20 enemy dismounted infantry in the open, over."