Fire support is defined by the United States Department of Defense as "Fires that directly support land, maritime, amphibious, and special operations forces to engage enemy forces, combat formations, and facilities in pursuit of tactical and operational objectives." Typically, fire support is provided by artillery or close air support (usually directed by a forward observer), and is used to shape the battlefield or, more optimistically, define the battle. Warships, for example, have long provided naval gunfire support. Artillery observers allow adjusting fire. Fire support has been used since the advent of cannons in warfare as artillery. Fire support, as an extension, is the marriage of artillery to the forces in contact. It is the direct ability to properly use artillery. It is distinct from direct fire, which is provided by the forces in contact.