Urban CAS operating environments typically range from small towns to large cities with corresponding extents of vertical development (e.g., tall buildings), population sizes, and cultural and community dynamics. During combat, aircraft commonly provide supporting firepower inoffensive and defensive operations to destroy, disrupt, suppress, neutralize, or delay hostile forces. The speed, range, maneuverability, and selection of integrated weapons systems of the aircraft involved allows CAS assets to attack targets that other friendly and allied forces may not be able to engage effectively (JCS 2014). When conditions for air operations are permissive, CAS can halt enemy attacks, help create breakthroughs, destroy targets, cover retreats, and guard flanks. While achieving these objectives, air and ground operations must be conducted in accordance with Department of Defense Directive 2311.01E, DoD Law of War Program and Rules of Engagement (ROEs), which specifies that U.S. military forces will adhere to the following guidelines:

• Act with proportionality, replying to hostility with only as much force as needed to eliminate the enemy

• Distinguish combatants from noncombatants, and distinguish military objectives from protected places to minimize collateral damage

• Prevent unnecessary suffering by safeguarding certain fundamental human rights of those involved in a conflict.

The planning and execution of Urban CAS missions is difficult because these missions either require or inevitably involve the following:

• operations in “urban canyons” (i.e., artificial canyons created by multistory buildings)

• deconfliction of multiple aircraft operating within a confined airspace

• operation in accordance with the ROEs

• difficulty in threat analysis because of information, environmental, and visibility constraints

• overload of visual cues associated with civilian traffic, presence of buildings, and varied landscape

• presence of noncombatants proximal to identified threats

• potential for collateral damage during engagement

• increased risk of friendly fire with other allied air and ground teams in the area (JCS 2014). These operational circumstances cause tactical difficulties in properly identifying and locating potential targets while discerning and protecting Friendly Forces (FFOR). Both are critical for successful execution of Urban CAS missions. Readiness for Urban CAS missions requires that air and ground crews train intensively to gain practical experience responding to the following situations:

• Loss of, or inability to maintain, communication. Urban terrain inhibits communications equipment and can absorb or reflect transmitted signals.

• Difficulty identifying targets. Vertical development makes it difficult for aircrews to identify target combatants and may require specific positioning and orientation attack headings to achieve line-of-sight with an identified target. Ground-level observers may be positioned on upper floors of buildings to improve visibility. In these situations, ground teams (e.g., JTACs) mark and designate their positions or CAS target locations visually with an infrared laser pointer, electronically with a Global Positioning System (GPS) grid, or with a gridded reference graphic to guide aircraft tracking.

• Difficulty maneuvering aircraft over urban terrain. Aircraft navigation over and through urban terrain can be more difficult than over natural terrain because maps do not show vertical development of urban terrain.

• Requirement for navigational aids. Rapid movement from position to position can create confusion between aerial and ground observers as to friendly and enemy locations. Familiarity with the characteristics of urban terrain allows aircrews to discern key features in this environment. Navigational aids, such as GPS, have reduced but not eliminated this challenge. The use of the GPS and handheld laser pointers or designators eases the problems associated with night navigation, orientation, and target identification.

• Conditions of limited visibility. Limited visibility may occur because of fog, smoke, or dust on the battlefield, but occurs most frequently because of operations extending into hours of darkness. Night navigation systems may be degraded because of interference induced by buildings and enemy GPS jamming equipment. Ability to provide CAS during times of limited visibility and adverse weather demands a higher level of proficiency that can only come about through dedicated, realistic CAS training. Aircrews and JTACs must routinely and consistently train together during such conditions to overcome visual limitations when the aircrew have only sensors and systems to guide them.

• Artificial lighting. Rapidly changing lighting conditions from day/night operations and the effects from operating within terrain with artificial lighting impacts how the target presents against its background and the measures required to ensure an aircrew can distinguish it from its surroundings. Additionally, the artificial lighting of urban environments can limit the usefulness of night vision equipment because lights from buildings, streets, airports, and industrial areas can create glare and reduce visibility (JCS 2014).