Rank Insignia Comments Field Marshal The rank evolved from the title of marescalci (masters of the horse) of the early Frankish kings. The importance of cavalry in medieval warfare led to the marshalship being associated with a command position.
The modern military title of field marshal was introduced into the British army in 1736 by King George II, who imported it from Germany. In Britain the rank came to be bestowed only upon a few senior army officers, notably the chief of Britain's Imperial General Staff.
General The King would be the commander but he might appoint a Captain General to command in his name - the first being George Monck appointed by Charles II in 1660. Later, when the title of Colonel became popular some Kings called their commanders Colonel General. The British Army stopped using the Captain part of the title by the Eighteenth Century leaving just General as the top commander. Lat. generalis "something pertaining to a whole unit of anything rather than just to a part". Before the Sixteenth Century armies were usually formed only when needed for a war or campaign. Lieutenant General The king or his Captain General would often be away from the army since they had interests elsewhere so the job of actually running the army fell to the Captain General's assistant - his lieutenant - the Lieutenant General. This was not a permanent rank until the Seventeenth Century, before which one of the Colonels might be appointed Lieutenant General for a particular campaign or war but he would still command his own regiment. Major General The army's chief administrative officer was the Sergeant Major General. He would be an experienced soldier, possibly a commoner, who served as chief of staff. For much of his administrative work he dealt with the regimental Sergeant Majors, thus his title meant "overall" or "chief" Sergeant Major. His duties included such things as supply, organization, and forming the army for battle or march.
As the General ranks became fixed during the Seventeenth Century the Sergeant portion fell away leaving the title as Major General. This happened in England in 1655 when its Lord Protector Oliver Cromwell organized the country into eleven military districts each commanded by a Major General.
Brigadier Commander of a Brigade, in some armies later known as a Brigadier General. The Lieutenant General and Sergeant Major General dealt directly with the Colonels who lead the regiments making up the army. When there got to be too many regiments for the two generals to handle effectively they organized Brigades, usually composed of three or more Regiments. During the nineteenth century and before the "rank" of Brigadier was actually established, a local or temporary appointment granted (typically) to a full Colonel when commanding a Brigade.
The Brigadier General was the lowest-ranking general officer but was abolished when the Brigade was abolished after World War I, being replaced by Colonels Commandant.. The rank of Brigadier appeared in 1928
Colonel The Spanish Army was organised into twenty units called colunelas or columns. These comprised1000 to 1250 men further organized into companies. The commander was the cabo de colunela, head of the column, or Colonel. Since the colunelas were royal or "crown" units they were also called coronelias and their commanders coronels.
The French developed Regiments from the colunela, keeping the title of Colonel and pronounced it the way it looks. The British copied the French. They also borrowed the Colonel from the French but adopted the Spanish pronunciation of coronel.
Lieutenant Colonel The Colonel's assistants - their Lieutenants - took over at such times and any other times the Colonels were gone. The Colonel's lieutenants, of course, soon became the Lieutenant Colonels. Major A Major was originally the Sergeant Major third in command to a Colonel in a traditional Regiment. Later, like a Lieutenant Colonel, a Major might command his own Battalion. Lat. maior is simply Latin for "greater". Captain Originally Captain-Lieutenant, becoming Captain in 1772. Lat. capitaneus "chieftain", from Lat. caput "head". Chieftain or head of a unit. As armies evolved his post came to be at the head of a company, which by the Sixteenth Century was usually 100 to 200 men. That seemed to be the number one man could manage in battle. Lieutenant French lieu (place) tenant (holder). The Lieutenant normally commands a small tactical unit such as a platoon. A Lieutenant often takes the place of a superior officer when that officer is absent. Second Lieutenant The lowest rank of commissioned officer. Note that a Subaltern is a term applied to any officer below the rank of captain, especially a second lieutenant. Derivation from Latin related to the word for alternate.
Until 1871 the lowest commissioned rank was the Ensign in the Infantry and Cornet in the Cavalry - both names derived from French words signifying standard bearers. The Fusilier regiments, having no company colours, had First and Second Lieutenants anyway. The Fusiliers abolished the rank of Second Lieutenant in 1834. Between 1871-1877 the lowest was the Sub Lieutenant, after which today's Second Lieutenant rank was established.
Warrant Officer Introduced into the British Army in 1879, the military grade of Warrant Officer dates back to the early years of the Royal Navy. These experienced soldiers, often have specialist appointments. They hold a Royal Warrant from Her Majesty The Queen. There are currently two classes of Warrant Officer, First Class and Second Class. Staff Sergeant A rank senior to sergeant. Sergeant Lat. serviens servant to a knight in medieval times. The English borrowed the word sergeant from the French in about the Thirteenth Century. Meaning "non-commissioned military officer" first recorded 1548. Originally a much more important rank than presently. Corporal Originally referred to a reliable veteran called the capo de'squadra or head of the square.
The title changed to caporale by the Sixteenth Century and meant the leader of a small body of soldiers. The French picked up the term in about the Sixteenth Century and pronounced it in various ways, one of them being corporal, which indicates a mixing with the Latin word corpus or French corps (body).
The British adopted corporal in the Seventeenth or Eighteenth Century and it has been a part of the army ever since. The British gave the Corporal his two stripes when they started using chevrons in 1803.
Lance Corporal Appointment and not a rank. Junior to a Corporal. From lancepesade "officer of lowest rank, from obsolete French lancepessade, from Old Italian lancia spezzata, superior soldier, literally "broken lance". Originally referred to as a "chosen man" who would take control of the section if the Corporal was to be killed or wounded Private Lat. privus or privo "an individual person and later an individual without (deprived of) an office" i.e. a private gentleman. The term as a military rank seems to come from the Sixteenth Century when individuals had the privilege of enlisting or making private contracts to serve as private soldiers in military units.
(SOURCE : VIA E-MAIL FROM CARL GOMES VET)