A General officer is an officer of high military rank. The term or equivalent is used by nearly every country in the world. General can be used as a generic term for all grades of general officer, or it can specifically refer to a single rank that is just called general.
The various grades of general officer are at the top of the rank structure; lower-ranking officers are known as field officers. The General Officer ranks came about by adding General as an adjective to existing names of ranks, although in some countries the highest general officers are titled Field Marshal or Marshal. All officers who commanded more than a single regiment (the most significant level of unit) came to be known as "general officers".
There are two common systems of using general ranks.
One form, the old European system, is used in the United Kingdom from which it eventually spread to the Commonwealth and the United States of America. The system is not British in origin, and variations of this system were once used throughout Europe.
The other is derived from the French Revolution, where generals' ranks are named according to the unit they (theoretically) command.
Old European system
|Field Marshal or Field Marshal General|
|General or Captain General|
|Sergeant Major General or Major General|
The system used either a brigadier rank, or a colonel general rank (i.e. exclude one of the italicised ranks.)
The rank of field marshal was used by some countries as the highest rank, while in other countries it was used as a divisional or brigade rank. Many countries (notably pre-revolutionary France and eventually much of Latin America) actually used two brigade command ranks, which is why some countries now use two stars as their brigade general insignia. (Mexico and Argentina still use two brigade command ranks.)
In some nations (particularly in the Commonwealth), the equivalent to Brigadier General is Brigadier, which is not always considered by these armies to be a general officer rank, although it is always treated as equivalent to the rank of Brigadier General for comparative purposes.
Note that a Lieutenant General outranks a Major General, although a (field) Lieutenant is outranked by a Major.
French (Revolutionary) system
Other nomenclatures for general officers include the titles and/or ranks:
In the Old European system, a General, without prefix or suffix (and sometimes referred to informally as a "full general"), is usually the most senior type of general, above Lieutenant General and directly below Field Marshal. Usually it is the most senior peace-time rank, with more senior ranks (for example, Field Marshal) being used only in wartime, or as honorary titles.
In some armies, however, the rank of Captain General, General of the Army, Army General or Colonel General occupied or occupies this position. Depending on circumstances and the army in question, these ranks may be considered to be equivalent to a full General or to a Field Marshal.
The rank of General came about as a "Captain-General", the captain of an army in general (i.e., the whole army). The rank of Captain-General began appearing around the time of the organization of professional armies in the 17th century. In most countries "Captain-General" contracted to just "General".
The following articles deal with the rank of General, or its equivalent, as it is or was employed in the militaries of those countries.
Some countries (such as the United States) use the General Officer ranks for both the army and the air force; others only use the General Officer ranks for the army, while in the air force they use Air Officers as the equivalent of General Officers. They use the air force rank of Air Chief Marshal as the equivalent of the specific army rank of General. This latter group includes the British Royal Air Force and those based on it (e.g. India, Pakistan, New Zealand, Nigeria etc.).
In most navies Flag Officers are the equivalent of General Officers, and the naval rank of Admiral is equivalent to the specific army rank of General. A noteworthy historical exception was the Cromwellian naval rank General at sea. In recent years in the American service there is a tendency to use "Flag Officer" and "Flag Rank" to refer to generals and admirals of the services collectively.