A more thorough explanation:

Definition: The rules and regulations that govern the activities of an army and navy. It is also the body of laws and procedures that governed the U.S. military until replaced in 1951 by the Uniform Code of Military Justice.

Examples:

• Rules about how soldiers should behave during wartime
• Regulations about how weapons should be used
• Procedures for handling prisoners of war

The examples illustrate how the articles of war provide guidelines for the behavior of military personnel during wartime. They ensure that soldiers and sailors act in a way that is consistent with the goals of the military and the laws of the country they serve. For example, rules about how weapons should be used help to prevent unnecessary harm to civilians and non-combatants. Procedures for handling prisoners of war ensure that they are treated humanely and in accordance with international law.