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 buildings of all sorts. Some civilians may be difficult to distinguish from combatants such as armed militias and gangs, particularly if individuals are simply trying to protect their homes from the 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 military term for urban warfare is UO an abbreviation for Urban Operations (MOUT, an abbreviation for Military Operations in Urban Terrain has been replaced by UO although the term MOUT Site is still in use). The British military term is OBUA (Operations in Built-Up Areas) or FIBUA (Fighting in Built-Up Areas) or sometimes FISH (Fighting In Someone's House) . The term FOFO (Fighting in Fortified Objectives) refers to clearing enemy personnel from narrow and entrenched places like bunkers, trenches and strongholds; the dismantling of mines and wires; and the securing of footholds in enemy areas.
The Battle of Bazeilles on 1 September 1870 during the Franco-Prussian war was one of the first instances of urban warfare. Regular French troops and Franc tireur partisans, equipped with the new Chassepot rifle allowing quick sniper fire, ambushed advancing Bavarians while hiding in houses, inflicting heavy losses.
Military operations in World War II often relied on large quantities of artillery fire and air support varying from ground attack fighters to heavy bombers. In some particularly vicious urban warfare operations such as Stalingrad and Warsaw, all weapons were used irrespective of their consequences. However, when liberating occupied territory some restraint was often applied, particularly in urban settings. For example, Canadian operations in both Ortona and Groningen avoided the use of artillery altogether to spare civilians and buildings.
Armies are bound by laws of war governing military necessity to the amount of force which can be applied when attacking an area where there are known to be civilians. Until the 1970s this was covered by customary law and IV Hague Convention "The Laws and Customs of War on Land" of 1907 and specifically articles 25-29. This has since been supplemented by the "Additional Protocols to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of International and Non-International Armed Conflicts". Sometimes distinction and proportionality, as in the case of the Canadians in Ortona causes the attacking force to restrain from using all the force they could when attacking a city. In other cases, such as the Battle of Stalingrad and the Battle of Berlin, both armies considered evacuating civilians only to find it impractical. When Russian forces attacked Grozny in 1999, large amounts of artillery fire was used. The Russian Army handled the issue of civilian casualties by warning the inhabitants that they were going to launch an all-out assault on Grozny and requested that all civilians leave the city before the start of the artillery bombardment.
Fighting in an urban landscape can offer some advantages to a weaker defending force or to guerrilla fighters. The attacking army must account for three-dimensions more often than two, and consequently expend greater amounts of manpower in order to secure a myriad of structures, (ferroconcrete structures will be ruined by heavy bombardment, but it is very difficult to totally demolish such a building when it is well defended), and mountains of rubble. Examples, of this type of problem for the attacking forces include the fighting for the Red October Steel Factory during the Battle of Stalingrad, and despite heavy bombardment with artillery at point blank range (with some pieces large as 203mm howitzers), Soviet forces had to fight room by room to capture the Reichstag in 1945. It is also difficult to destroy underground or heavily fortified structures such as bunkers and utility tunnels. For example during the Battle of Budapest in 1944 fighting broke out in the sewers, as both Axis and Soviet troops used them for troops movement.
The characteristics of an average city include tall buildings, narrow alleys, sewage tunnels and possibly a subway system. Defenders may have the advantage of detailed local knowledge of the area, right down to the layout inside of buildings and means of travel not shown on maps. The buildings can provide excellent sniping posts while alleys and rubble-filled streets are ideal for planting booby traps. Defenders can move from one part of the city to another undetected using underground tunnels and spring ambushes. Meanwhile, the attackers tend to become more exposed than the defender as they must use the open streets more often, unfamiliar with the defenders' secret and hidden routes. During a house to house search the attacker is often also exposed on the streets.
A Soviet combat group was a mixed arms unit of about eighty men in assault groups of six to eight men, closely supported by field artillery. These were tactical units which were able to apply the tactics of house to house fighting that the Soviets had been forced to develop and refine at each festung stadt (fortress city) they had encountered from Stalingrad to Berlin.
The Germans tactics used for the urban warfare that took place in Berlin was dictated by three considerations. These were: the experience that the Germans had gained during five years of war; the physical characteristics of Berlin; and the tactics used by the Soviets. Most of central districts of Berlin consists of city blocks with straight wide roads with several waterways, parks and large railway marshalling yards. It is predominantly flat but there are some low hills like that of Kreuzberg that is 66m above sea level. Much of the housing stock consisted of apartments blocks built in the second half of the 19th century most of those, thanks to housing regulations, and few elevators, were five stories high built around a courtyard which could be reached from the street through a corridor large enough to take a horse and cart or the small trucks used to deliver coal. In many places these apartment blocks were built around several courtyards one behind the other each one reached through the outer courtyards by a ground level tunnel similar to that between the first courtyard and the road. The larger more expensive flats faced the street and the smaller less expensive ones could be found around the inner courtyards.
Just as the Soviets had learned a lot about urban warfare, so had the Germans. The Waffen SS did not use the makeshift barricades erected close to street corners, because these could be raked by artillery fire from guns firing over open sights further along the straight streets. Instead they put snipers and machine guns on the upper floors and the roofs because the Soviet tanks could not elevate their guns that high and they put men armed with panzerfausts in cellar windows to ambush tanks as they moved down the streets. These tactics were quickly adopted by the Hitler Youth and the First World War Volkssturm veterans.
To counter these tactics the Soviets mounted sub-machine gunners on the tanks who sprayed every doorway and window, but this meant the tank could not traverse its turret quickly. The other solution was to rely on heavy howitzers (152mm and 203mm) firing over open sights to blast defended buildings and to use anti-aircraft guns against the German gunners on the higher floors. Soviet combat groups started to move from house to house instead of directly down the streets. They moved through the apartments and cellars blasting holes through the walls of adjacent buildings (for which the Soviets found abandoned German panzerfausts were very effective) while others fought across the roof tops and through the attics. These tactics took the Germans lying in ambush for tanks in the flanks. Flamethrowers and grenades were very effective, but as the Berlin civilian population had not been evacuated these tactics inevitably killed many civilians.
During the First Chechen War most of the Chechen fighters had been trained in the Soviet armed forces. They were divided into combat groups consisted of 15 to 20 personnel, subdivided into three or four-man fire teams. A fire team consisted of an antitank gunner, usually armed with Russian made RPG-7s or RPG-18s, a machine gunner and a sniper. The team would be supported by ammunition runners and assistant gunners. To destroy Russian armoured vehicles in Grozny, five or six hunter-killer fire teams deploy at ground level, in second and third stories, and in basements. The snipers and machine gunners would pin down the supporting infantry while the antitank gunners would engage the armoured vehicle aiming at the top, rear and sides of vehicles.
Initially the Russians were taken by surprise, and their armoured columns, that were supposed to take the city without difficulty, as Soviet forces had taken Budapest in 1956, were decimated in fighting more reminiscent of the Battle of Budapest in late 1944. Like their forefathers in Berlin, as a short term measure they deployed self-propelled anti-aircraft guns (ZSU-23-4 and 2K22M) to engage the Chechen combat groups, as their tank's main gun did not have the elevation and depression to engage the fire teams and an armoured vehicle's machine gun could not suppress the fire of half a dozen different fire teams simultaneously. In the long term the Russians brought in more infantry and began a systematic advance through the city, house by house and block by block with dismounted Russian infantry moving in support of armour. In proactive moves the Russians started to set up ambush points of their own and then move armour towards them to lure the Chechen combat groups into ambushes.
As with the Soviets tank crews in Berlin in 1945, who attached bedsprings to the outside of their turrets to reduce the damage done by German panzerfausts, some of the Russian armour was fitted quickly with a cage of wire mesh mounted some 25-30 centimetres away from the hull armor to defeat the shaped charges of the Chechen RPGs.
The term close-quarter battle refers to fighting methods within buildings, streets, narrow alleys and other places where visibility and maneuverability are limited.
Both close-quarters-battle (CQB) and urban operations (UO) are related to urban warfare, but while UO refers mainly to the macromanagement factor (i.e. sending troops, using of heavy armoured fighting vehicles, battle management), CQB refers to the micromanagement factor—namely: how a small squad of infantry troops should fight in urban environments and/or inside buildings in order to achieve its goals with minimal casualties.
As a doctrine, CQB concerns topics such as:
It should be noted that military CQB doctrine is different from police CQB doctrine, mainly because the military usually operates in hostile areas while the police operates within friendly populations.
Armies that often engage in urban warfare operations may train most of their infantry in CQB doctrine.