The Articles of War are a set of regulations drawn up to govern the conduct of a country's military and naval forces. The first known usage of the phrase is in Robert Monro's 1637 work His expedition with the worthy Scot's regiment called Mac-keyes regiment etc. (in the form "Articles of warres") and can be used to refer to military law in general. In Swedish, the equivalent term Krigsartiklar, is first mentioned in 1556. However, the term is usually used more specifically and with the modern spelling and capitalisation to refer to the British regulations drawn up in the wake of the Glorious Revolution and the United States regulations later based on them.

United Kingdom

Throughout the Articles' existence, there were separate sets for the army and navy.

Royal Navy

England's first Articles of War were written for the Royal Navy. They formed the statutory provisions regulating and governing the behaviour of members of the Royal Navy. They were prominently displayed in all naval ships, and set out a list of criminal provisions which applied to members of the Royal Navy and others to whom the Act applied, in addition to the criminal law of England and Wales and any local criminal law. The naval Articles of War were originally issued by the Lords Commissioners of the Admiralty in 1653 as fighting instructions after defeat at the Battle of Dungeness. Soon after the Restoration, they were converted into an Act of Parliament. After another defeat at the Battle of Toulon, Parliament amended the Articles in 1749, further tightening discipline. These Articles resulted in the execution of Admiral John Byng, despite a clear sentiment in the navy and in Parliament that he should be given a lower punishment. In response, the 1779 amendment was the start of a gradual process of easing the more draconian punishments. The naval Articles were retained in the Naval Discipline Act 1957 but then replaced by the provisions of the tri-service Armed Forces Act 2006. The following articles and orders were established from the 25th of December 1749; and are directed to be observed and put in execution, as well in time of peace as in time of war.

British Army

The first set of Articles of War for the English Army, from 1707 the British Army, were written under William III (William of Orange) (r.1689–1702), taking the place of the medieval Rules and Ordinances of War, a list of regulations issued by the king at the beginning of every expedition or campaign. The Mutiny Acts empowered the king de jure and his government de facto to govern their army by creating a set of Articles of War for each conflict. To a large degree, they were superseded by King's Regulations in force at all times. The Articles of War fell out of use by the Army when they were omitted from the Army Act 1955 (3 & 4 Eliz. 2. c. 18).

United States

On 30 June 1775, the Second Continental Congress established 69 Articles of War to govern the conduct of the Continental Army. Effective upon ratification in 1789, Article I, Section 8 of the U.S. Constitution provided that the Congress has the legislative power to regulate the land and naval forces. On 10 April 1806, the U.S. Congress enacted 101 Articles of War (for the Army and the Navy), which were not revised until the American Civil War. The 1806 Articles of War were revised with the Lieber Code (1863), to legally allow the Union Army to combat Confederate guerrillas and enemy civilians during the Civil War. On 4 June 1920, Congress enacted 121 Articles of War that went into effect on 4 February 1921 with the exception of Articles 2, 23, and 45, which became effective immediately. The military justice system then continued to operate under the Articles of War until 31 May 1951, when the Uniform Code of Military Justice came into effect.