This is basically a quick guide to the military ranks typically seen for land forces in fantasy settings. While many of the ranks continue to be used today, fantasy armies typically have a much more simplified organization.
Recruit - An inexperienced soldier.
Veteran - An experienced soldier.
Corporal - A non-commissioned officer (NCO or Noncom) given authority over other soldiers.
Sergeant - A senior NCO.
Sergeant Major (or Master Sergeant) - Generally, the most senior NCO within a particular unit.
Warrant Officer - This is an intermediary rank between enlisted and officer typically applied to specialists. For units such as artillery/siege equipment, groups of sappers, surveyors, or pioneers.
Adjutant (assistant) - This the title for an officer who serves as an assistant to a more senior officer.
Lieutenant - The lowest rank of officer. Considered to be the lowest rank of company-grade officers and often found in command of a platoon.
Commander - An intermediate officer rank. Company-grade officers of this rank often serve as the executive officer of a company.
Captain - A bit higher on the officer chain, captains are the senior rank of company-grade officers, and are generally found commanding companies.
Major - The lowest rank of field-grade officers, majors are generally employed as aides to generals or commanding battalion-sized units in their own right.
Colonel - a higher rank of field-grade officer, generally employed as regimental commanders.
General - The lowest of the flag rank officers, commanding divisions.
Marshal - Senior flag ranked officer, often in command of an entire military force consisting of several divisions, called a corps.