A battlefield, battleground, or field of battle is the location of a present or historic battle involving ground warfare. It is commonly understood to be limited to the point of contact between opposing forces, though battles may involve troops covering broad geographic areas. Although the term implies that battles are typically fought in a field – an open stretch of level ground – it applies to any type of terrain on which a battle is fought. The term can also have legal significance, and battlefields may have substantial historical and cultural value—the battlefield has been described as "a place where ideals and loyalties are put to the test". Various acts and treaties restrict certain belligerent conduct to an identified battlefield. Other legal regimes promote the preservation of certain battlefields as sites of historic importance. Modern military theory and doctrine has, with technological advances in warfare, evolved the understanding of a battlefield from one defined by terrain to a more multifaceted perception of all of the factors affecting the conduct of a battle and is conceptualised as the battlespace. The occurrence of a battle at a particular location may be entirely accidental, if an encounter between hostile forces occurs with neither side having expected the encounter. Typically, however, the location is chosen deliberately, either by agreement of the two sides or, more commonly, by the commander of one side, who attempts to either initiate an attack on terrain favorable to the attack, or position forces on ground favorable to defense, if anticipating an attack. Although many battlefields arise in the course of military operations, there have been a number of occasions where formal conventions have ordained the nature and site of the battlefield. It has been suggested, on the basis of anthropological research, that ritual warfare involving battles on traditional "fighting grounds", bound by rules to minimise casualties, may have been common among early societies.