Colonel Colonel , abbreviated Col , is a military rank of a senior commissioned officer . It or a corresponding rank exists in most armies , marine forces and in many air forces ; the naval equivalent rank is generally captain . In air forces with a separate rank structure , the equivalent rank is generally group captain . It is also used in some police forces and other paramilitary rank structures . A colonel was typically in charge of a regiment in an army , especially in Great Britain ; but typically as of 2012 a colonel is the commander of a brigade or regiment in the U . S . Army or Marine Corps , and of a group or wing in the US Air Force . ' Colonel ' is usually the highest or second - highest field rank , and is below the general ranks . In some militaries , no ' general ' ranks exist and colonel is the highest - ranking military officer . History and origins . With the shift from primarily mercenary to primarily national armies in the course of the seventeenth century , a colonel ( normally a member of the aristocracy ) became a holder ( German " Inhaber " ) or proprietor of a military contract with a sovereign . The colonel purchased the regimental contract — the right to hold the regiment — from the previous holder of that right or directly from the sovereign when a new regiment was formed or an incumbent was killed . The rank of colonel was popularized by the Spanish tercios in the 16th and 17th centuries . Gonzalo Fernández de Córdoba , nicknamed ' the Great Captain ' , divided his armies in ' coronelías ' or colonelcies , each led by a ' coronel ' or colonel . The modern English pronunciation of the word is due to the first variant . The use of ' colonel ' became more widespread as the tercios led by commanders of many nationalities fought all over Europe . As the office of colonel became an established practice , the colonel became the senior captain in a group of companies which were all sworn to observe his personal authority — to be ruled or regimented by him . This regiment , or governance , was to some extent embodied in a contract and set of written rules , also referred to as the colonel ' s regiment or standing regulation ( s ) . By extension , the group of companies subject to a colonel ' s regiment ( in the foregoing sense ) came to be referred to as his regiment ( in the modern sense ) as well . In French usage of this period the senior colonel in the army or , in a field force , the senior military contractor , was the colonel general and , in the absence of the sovereign or his designate , the colonel general might serve as the commander of a force . The position , however , was primarily contractual and it became progressively more of a functionless sinecure . ( The head of a single regiment or demi brigade would be called a ' mestre de camp ' or , after the Revolution , a ' chef de brigade ' . ) By the late 19th century , colonel was a professional military rank though still held typically by an officer in command of a regiment or equivalent unit . Along with other ranks it has become progressively more a matter of ranked duties , qualifications and experience and of corresponding titles and pay scale than of functional office in a particular organization . As European military influence expanded throughout the world , the rank of colonel became adopted by nearly every nation under a variety of names . With the rise of communism , some of the large communist militaries saw fit to expand the colonel rank into several grades , resulting in the unique senior colonel rank which was found and is still used in such nations as China and North Korea . Colonel - in - chief . In many modern armies the ' regiment ' has more importance as a ceremonial unit or a focus of members ' loyalty than as an actual battle formation . Troops tend to be deployed in ' battalions ' ( commanded by a lieutenant colonel ) as a more convenient size of military unit and , as such , colonels have tended to have a higher profile in specialist and command roles than as actual commanders of regiments . However , in Commonwealth armies the position of the colonel as the figurehead of a regiment is maintained in the honorary role of " colonel - in - chief " , usually held by a member of the royal family , the nobility , or a retired senior military officer . The colonel - in - chief wears a colonel ' s uniform and encourages the members of the regiment , but takes no active part in the actual command structure or in any operational duties . Colonel and equivalent ranks by country . Colonel in individual military forces . The following articles deal with the rank of colonel as it is used in various national militaries . European equivalent ranks . Since the 16th century , the rank of regimental commander was adopted by several Central and Eastern European armies , most notably the forces of Polish - Lithuanian Commonwealth , Cossacks and then Muscovy . In countries with Slavic languages , the exact name of the rank maintains a variety of spellings , all descendant from the Old Slavonic word " plk " or " polk " meaning " unit of standing army " ( see The Tale of Igor ' s Campaign ) , and include the following : Colonel as highest ranking officer . Some military forces have a colonel as their highest - ranking officer , with no ' general ' ranks , and no superior authority ( except , perhaps , the head of state as a titular commander - in - chief ) other than the respective national government . Examples include the following ( arranged alphabetically by country name ) : Other uses of colonel ranks . The term " colonel " is also used as a title for auctioneers in the United States ; there are a variety of theories or folk etymologies to explain the use of the term . One of these is the claim that during the American Civil War goods seized by armies were sold at auction by the colonel of the division . Kentucky colonel is the highest title of honor bestowed by the Commonwealth of Kentucky . Commissions for Kentucky colonels are given by the Governor and the Secretary of State to individuals in recognition of noteworthy accomplishments and outstanding service to a community , state or the nation . The sitting governor of the Commonwealth of Kentucky bestows the honor of a colonel ' s Commission , by issuance of letters patent . The rank of Colonel is also used by some military police forces such as Brazilian Military Police and the Carabineros de Chile .