When thinking about war, many tend to think about jungle or open areas like trying to take a trench or hill, but what about getting up close?
Urban warfare or close quarter combat had not play a major role in history as war was mostly fought in big open terrians. Although there were minor events of urban warfare during the musket times and World War one and two, some of the first major events of urban warfare occured during the Battle of Berlin during the last days of the Third Reich. Soviet troops were advancing house to house, street to street, alleyway to alleyway. Using their experience from the Battle of Stalingrad, the Soviet troops knew better than the Germans and advanced in a fast pace.
The US military did not have much experience in urban warfare until the Battle of Hue in 1968 during the Tet Offensive. Hue is an historical city and is the home of Vietnamese culture. It was one of the few cities left untouched during the Vietnam War until the Tet Offensive when the Viet Cong took over the city. Because it was a special historical city, bombing and artillery was not allowed in order to preserve the city. Without support and experience, the marines had a hard time. Sometimes it took half a day to move from one side of the street to the other. The US military experienced major urban warfare again during the war in Iraq especially the Battle of Fallujah where both US soldiers and marines had to take over city full of insurgents who earlier ambushed and killed four American PMCs and mutilated them on TV.
Urban warfare is considered chaotic as soldiers have to clear every room and every corner. The biggest danger is that there could be an insurgent around any corner waiting to kill. There are also the danger of booby traps, trap doors, hidden entrances, machine gun pits and grenades. Sometimes it may take a company of 100 soldiers to clear four houses.
To have equipment suitable for urban combat, there are guns like the MP5 which uses the 9mm pistol round. It is great for close quarters but the is unsuitable for long range and body armor. To fix this problem of not penetrating body armor, the MP7 was developed with it's 4.6mm round that can do the job. The UMP-45 has the .45 caliber which unlike the 9mm , has a wider diameter plus extra stopping power which can stop an insurgent dead in his track. The .45 caliber was first used on the M1911 pistol which responded to complaints from US soldiers facing deadly enemies in the Philippines not going down after being hit from the 9mm. Of course, submachine guns may not be enough for urban warfare and may require guns with heavier caliber like the 5.56mm. In this case the M4 Carbine was developed for close quarters, in other words, shorter barrel. When advancing in battle, soldiers tend to advance sideways to make themselves a smaller targer which also reduce their chances of being hit. With the introduction of body armor, advancing sideways is not recommended as the side of the vest has little or no armored plates. Therefore, SWAT members advance facing frontwards with their body armor protecting them.
When dealing with the dangers of close quarters, there had been several techniques developed like "slicing the pie" which meant slowly maneuvering slowly around the corner making sure the sight is clear before moving. Small flashlights can be used which can be attached on the gun or used on another hand. They are used to see through dark places but only recommended when doing a quick search otherwise it will give away it's position. It can also be used as defence like barricading yourself in a room and shining your light on the door so when the intruder breaches the door, the first thing he sees is a bright wall of light. The British SAS attach their flashlights under the barrel of their MP5s and "where you point the torch, is where the bullets will end up". In hostage situations, flashbangs/stun grenades are used. They produce a bright light which temporarily blind a terrorist and produce a loud bang which is as loud as a jet engine which temporarily deafens the terrorist. The flashbang provide an extra few vital seconds to identifiy the terrorists and hostages. The Israelis invented a new weapon called the cornershot which can turn around corners. It has a camera and an LCD screen so a soldier can see what is around the corner without exposing himself. The Israelis also cleverly invented the concept of having the fake kitten attached on the cornershot so the terrorist is distracted giving the soldier a few extra seconds to identify and make the next decision. Lasers attached on guns are also used for pinpoint accuracy. When maneuvering around corners, experts highly recommend raising your arm (not holding the weapon) and use it to block any surprise attacks when encountering an enemy around a corner. By blocking his attack, you're prevented him from disarming you.
When breaching doors, a Ramington 870 "Little pig" shotgun is used with special rounds designed to push locks out. There are other ways of entry like using a battering ram or a Thor to bash the door open. Frame charges are used in blowing through walls or windows as a way of surprise entry instead of going through a door that could be barricaded. It is always important that when entering room, a soldier never goes in alone. To make sure he is going to be backed up without talking, he gives a nod meaning he is ready. The second soldier squeezes his shoulder shoulder indicating that he is also ready.
Room clearance is always part of urban warfare and is highly dangerous. Because of this, team work is vital. The door is known as the "fatal funnel" which has to be cleared quickly upon entering. When entering the room, there are areas of responsibilities, i.e. - the first soldier entering scans the right side while the next soldier scans the left side. They enter almost simultaneously so all areas of the room is scanned plus soldiers can watch each other's back. It is impossible for a soldier to scan 180 degrees at the same time. If the first soldier responsible for the right sector sees an enemy on the left, he must ignore him and trust the second soldier with his life that he will take care of the threat. If the first soldier decides to deal with the threat, not only he had ignored his area of responsibility, but put the lives of himself and his comrades at dangerous risk as there could be an enemy hiding at his sector waiting to open fire. Positioning is important because if a soldier's gun is jammed or misses and is in his comrade's line of fire (does not have a clean shot), then the situation can become fatal. So if you thought that soldiers/SWAT teams have an easy job of just going through room by room blazing at fully automatic, think again.