a. Cities. When defending in cities or other built-up areas, a battalion’s or company's combat formation can be in one or two echelons. Two-echelon formations are the most common. The combat formation may include a reserve (even in a two-echelon formation) and armored groups to provide mobile firepower and ambushes. Battalions can form assault groups in their second echelon, identical in strength and structure to those used in the attack. These are used to recover any key buildings captured by the BLUFOR.

    The forward edge of the defense is established on the outskirts of the town, or out in the country if it is required to hold dominating ground. A security zone is often organized outside the town. The mechanized infantry battalion and mechanized infantry company are the basic building blocks of the defense, and they receive strong reinforcements. Tanks and most of the supporting artillery are given to mechanized infantry elements to provide direct fire from strongpoints, covering any reasonable field of fire.

    Antitank weapons are positioned to cover road junctions and to fire along streets. Engineer assets are incorporated down to company level to assist in fortifying buildings, creating obstacles and improving routes between strongpoints. Strongpoints are expected to continue to resist even when encircled; additional reserves of ammunition and other supplies can be pre-positioned to provide a considerable measure of tactical independence.

    b. Mountains. In mountain areas, the defender can hold a wider frontage than in normal terrain, but also faces extra difficulties in organizing his defenses. In particular, the lack of roads restricts maneuver, and the defense is based on separate strongpoints established to hold vital ground such as commanding heights, passes road junctions and river crossings. On plateaus and in wide valleys the defense is organized normally.

    A two-echelon defense is standard in mountain areas, although in sectors unsuitable for armored movement the defense may be organized in one echelon, with a reserve. A minimum of resources is allocated to terrain unsuitable for any movement. Strongpoints are organized for all-around defense. Reconnaissance patrols, obstacles, demolitions, and ambushes cover the intervals between them.

    The OPFOR makes effective use of ambushes in mountain operations, not only in gaps between positions, but in front of them and in depth. Holding the ground dominating the approaches, with part of the defending force deployed in the pass itself covers mountain passes. Obstacles and mines are laid on the road through the pass and covered by crossing fire. Crossing fire from either side covers narrow canyons.

    c. Deserts. Deserts offer mixed terrain, with areas capable of supporting high rates of movement interspersed with soft sand, and dunes that restrict movement. Defense sectors are often wider than usual. The OPFOR practice is to cover the most likely axes with battalion defensive areas and company strongpoints, organized for all-around defense, and accept greater intervals than usual between them. Strong second echelons or reserves are held to counterattack or reinforce threatened sectors. The improvement of maneuver routes is a vital engineer task in desert warfare.

    The openness of desert terrain offers longer fields of view and fire. Reconnaissance is organized in greater depth than normal and direct fire weapons are effective at longer ranges, making it possible to increase unit frontages. High-precision weapons are more effective in such terrain, and special attention must be paid to camouflage and concealment.

    Defenses are organized in greater depth in the desert. Distances between echelons are greater and forces more dispersed. Reserves, mainly tank-heavy, are held in greater depth than usual and may be employed to counter BLUFOR enveloping movements. Mechanized infantry unit frontages in the forward area are similar to those in the normal defense. Mechanized infantry companies normally organize in a single echelon. Divisions and brigades may defend independently. Mined sectors and areas of limited trafficability may be lightly defended; only mobile patrols or outposts may cover them.

    Fortification work is much more difficult in deserts. Soft sand needs reinforcement, and there is generally a shortage of local material to use in preparing defenses. Strong winds blowing sand and dust mean that great care is required to keep all equipment and weapons serviceable. Laying mines is difficult in many sectors, and even when minefields are laid, they must be inspected regularly to check to see that they have not been exposed by the wind.