A commander-in-chief is the person or body that exercises supreme operational command and control of a nation's military forces or significant elements of those forces. In the latter case, the force element is those forces within a particular region, or associated by function. As a practical term, it refers to military competencies that reside in a nation-state's executive leadership—either a head of state, a head of government, a minister of defence, a national cabinet, or some other collegial body. Often, a given country's commander-in-chief (if held by an official) need not be or have been a commissioned officer or even a veteran. This follows the principle of civilian control of the military.The role of commander-in-chief derives from the Latin, imperator. Imperatores of the Roman Republic and Roman Empire possessed imperium (command) powers. In its modern use, the term first applied to King Charles I of England in 1639. A nation's head of state (monarchical or republican) usually holds the nominal position of commander-in-chief, even if effective executive power is held by a separate head of government. In a parliamentary system, the executive branch is ultimately dependent upon the will of the legislature; although the legislature does not issue orders directly to the armed forces and therefore does not control the military in any operational sense. Governors-general and colonial governors are also often appointed commander-in-chief of the military forces within their territory.A commander-in-chief is sometimes referred to as Supreme Commander, which is sometimes used as a specific term. The term is also used for military officers who hold such power and authority, not always through dictatorship, and as a subordinate (usually) to a head of state (see Generalissimo). The term is also used for officers that hold authority over individual branches or within a theatre of operations.