FIBUA

Urban warfare is combat conducted in urban areas such as towns and cities. Urban combat is very different from combat in the open at both the operational and tactical level. Complicating factors in urban warfare include the presence of civilians and the complexity of the urban terrain. Urban combat operations may be conducted in order to capitalize on the strategic or tactical advantages with which possession or control of a particular urban area gives or to deny these advantages to the enemy. Fighting in urban areas negates the advantages that one side may have over the other in armour, heavy artillery, or air support. Ambushes laid down by small groups of soldiers with handheld anti-tank weapons can effectively destroy entire columns of modern armour (as in the First Battle of Grozny), while artillery and air support can be severely reduced if the 'superior' party wants to limit civilian casualties as much as possible, but the defending party does not (or even uses civilians as human shields).

Some civilians may be difficult to distinguish from combatants such as armed militias and gangs, and particularly individuals who are simply trying to protect their homes from attackers. Tactics are complicated by a three-dimensional environment, limited fields of view and fire because of buildings, enhanced concealment and cover for defenders, below-ground infrastructure, and the ease of placement of booby traps and snipers.

The United States Armed Forces term for urban warfare is UO, an abbreviation for urban operations. The previously used U.S. military term MOUT, an abbreviation for military operations in urban terrain, has been replaced by UO, although the term MOUT Site is still in use.

...
Wikipedia