Doctrine provides a military organization with a common philosophy, a language, a purpose, and unity of effort. To this end, FM 3-06 discusses major Army operations in an urban environment. This environment, consisting of complex terrain, a concentrated population, and an infrastructure of systems, is an operational environment in which Army forces will operate. In the future, it may be the predominant operational environment. Each urban operation will be distinct from any other-any other urban operation as well as similar types of operations in other environments. Each operation will differ because of the multitude of combinations presented by the threat, the urban area itself, the major operation of which it may be part (or the focus), and the fluidity of societal and geo-political considerations. Therefore, there will always exist an innate tension between Army doctrine, the actual context of the urban operation, and future realities. Commanders are responsible to strike the proper balance between preparing for future challenges and maintaining the capability to respond to current threats.