Given ongoing events in Ukraine, the age-old adage that offense is the best defense is being put to the test. So far, throughout the country's towns and cities, the answer seems to be "not so much".
With that being said, history gives us ample examples and wisdom on how best to handle urban combat in general and urban defense in particular. Fighting in such environments is a very different beast to combat in other types of landscapes, and it raises unique challenges, as well as offering its own set of options and opportunities. Many of these are related to the huge availability of solid cover and line-of-sight denial. Others arise from the way cities naturally funnel pedestrian and vehicle traffic, constraining them to known and predictable avenues.
So today, we will go through wisdom gathered painfully, at great cost of human lives and material damage over history, on how defenders can best employ built environments against attackers.
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In olden days, architects would design fortresses so that the defenders would have as much of an advantage over attackers as possible. The first and most obvious advantage is the physical protection afforded by thick, sturdy walls.
While most buildings today aren't built to repel invaders, they do offer sturdy bases that defenders can use when bracing for an attack. Structures erected from concrete and rebar are especially tough and can act as impromptu fortifications. Most government buildings, apartment blocks, and office complexes are ideal for this role, as are banks.
If defenders have enough time to dig in, such buildings should be reinforced with materials such as lumber, steel girders, or sandbags. Such elements should be used to protect the structure from direct damage, help maintain integrity after damage is inflicted on the building, or cover areas through which attackers can enter the perimeter. Ideally, combat engineers would carry out reinforcement works, but if they are not available, civilians can fill the role partially.
Mines, barbed wire, and other physical barriers can also be used to deny attackers entry points into the building and make it hard for them to approach the site. Furniture, rubble, barbed wire, and mines should also be used to block or limit access to stairways and elevators; even if these do not neutralize any of the attackers, they can still delay a fighting force massively. Such makeshift defenses require a lot of time, effort, and resources (such as explosives and specialized combat engineers) to remove.
Inside the building itself, reinforcing materials should be used to create bunkers or similar fighting compartments that break a building's open floors into multiple areas of overlapping fire.
Like for ancient fortresses, however, the key to picking the right building to fortify is location. Strongpoints should have a good command of their surroundings (direct line of sight for soldiers to fire). Several close-together buildings can be fortified to ensure overlapping fields of fire that the enemy cannot hide from. Whether fortified alone or in groups, these buildings should be surrounded by obstacle courses that prevent attackers from simply bypassing them, or isolating the strongpoint from support from other defending units.
Heavy weapons such as rocket launchers, guns, automatic cannons, and heavy machine guns can also benefit from an elevated position from which to fire. Such weapons can be disassembled, carried to upper floors, and reassembled for use. Equipment such as this can allow defenders to halt entire armored columns.
A single fortified building can completely blunt even an armored assault, or at least stall it. One such building -- known today as "Pavlov's House" -- became famous during the Battle of Stalingrad in 1942. A platoon led by Sergeant Yakov Pavlov held out in this house against the German army for 60 days, repelling infantry and armored attacks. The soldiers surrounded the building with barbed wires and mines, broke holes through the interior walls to allow for movement, dug machinegun emplacements in the building's corners, and used the top floors to lay down anti-tank rifle fire on advancing tanks. When artillery would fire on the building, they retreated to the safety of the cellar, only to re-emerge and continue fighting.
Such stories illustrate just how hard it can be for attackers to negotiate a single fortified building. Still, modern battlefields involve systems that were not available during World War II, so one extra element should be considered:
The advent of modern surveillance systems such as drones, satellites, and reconnaissance planes, together with the precision weapons in use today, means that strongpoints are at risk of precision strikes. Concealment saves lives, so defenders should take steps to hide their exact position and activity as much as possible.
Citizens embroiled in the Syrian conflict would routinely hang large pieces of cloth, tarps, or sheet metal in between buildings to hide personnel from snipers and aircraft. Such measures are disproportionally effective compared to their simplicity. Soldiers rely on sight heavily on the battlefield and don't generally shoot unless they have reliable knowledge of where the enemy might be. In the case of heavy weaponry such as tank- or aircraft-mounted munitions, this is even more true. A pilot is much less likely to drop a bomb without a clear sighting than a soldier is to fire a single shot.
Even if the enemy chooses to fire, concealment measures still bring value to defenders. A weapon fired at an empty emplacement is effectively wasted, and cannot be used against an active defender -- contributing to the so-called 'virtual attrition' of the attacking forces.
Concealment measures should be used in conjuncture with fortifications to hide the defenders' movements and decrease the efficacy of enemy fire. Even so, a big fortified apartment building is hard to hide, and will undoubtedly draw some heavy ordinance its way. So another element should be considered to ensure the safety of defending soldiers.
Mouseholes are openings cut out to allow soldiers easy access through the interior as well as exterior walls of a building. They have been a mainstay of urban combat ever since the advent of gunpowder weaponry. Mouseholes can be created using explosives or simple tools, and should comfortably fit a soldier so as not to clog traffic during a tense situation. In the case that a building should be run over by the attackers, defenders can also use mouseholes as chokepoints to contain the enemy's advance by covering them with machine-gun fire or personal weapons.
Tunnels, on the other hand, are dug underground. They require significantly more work than mouseholes but have the added benefit of concealing and protecting troops that transit them from fire. Due to their nature, tunnel networks are hard to set up, so they should be used to allow strategic access to important sites and give defenders safe avenues of reinforcing strongpoints. Whenever possible, defenders should work to build extensive tunnel networks to give troops safe avenues of passage on the battlefield.
Underground transportation avenues and infrastructure, such as metro lines or sewage lines, can also be used as tunnels and bunkers. German soldiers used them to great effect during the Battle of Berlin in 1945 to cause great pain to Soviet soldiers moving into the city. Such infrastructure is usually roomy enough to also be usable as hospital and storage space, is extensive enough to act as a communications network, and offers an ideal setting to set up ambushes, bunkers, or counter attacks. Some can even allow for the passage of armored vehicles. They are also sturdy enough -- and dug deep enough underground -- to withstand most artillery and airstrikes.
But what about other areas of the city?
As daunting as fortified spaces can be, the fact of the matter is that not every building can be fortified. There simply isn't enough time, manpower, and material available when preparing a defense. But not every area needs to be fortified to help stop an attack. Sometimes, it's as simple as tearing buildings down.
Defenders have the advantage that they can use the terrain in their favor to a much greater extent than attackers. They are the first of the two sides to hold a position, they know the land, and can take up the best spots to punish any invaders. Rubbling buildings can help in this regard on several levels.
First, rubble presents a physical barrier that an invading army will have difficulty navigating and removing. This is especially true for concrete or brick rubble produced by demolishing buildings. It forces attackers to move through pre-determined areas, where defenses can be set up to stop their advance. It also prevents them from using all their firepower on a single objective as it prevents direct fire. Rubble serves to also block line of sight, thus limiting the ability of an attacking force to keep tabs on what the defenders are doing.
Rubbling is, understandably, a very damaging process and thus quite regrettable to use. But it does bring huge benefits to defenders by allowing them to alter the landscape to their purposes.
Although less effective than rubbling at containing an enemy's movements, barricades can be surprisingly effective at stopping both infantry and armored vehicles. Furniture, tires, sandbags, metallic elements, and wire all make for good barricades.
Urban landscapes are also very rich in objects that can be used for barricades such as trash containers, cars, manholes, industrial piping, and so forth. These should be used liberally and ideally set up in areas where defenders can unleash fire on any attackers attempting to navigate or remove them.
These aren't very common in cities, but any checkpoint or protected infrastructure site might have some of these barriers. If you have time and concrete to spare, makeshift barriers can also be quite effective. They usually come in 3ft / 1 m tall anti-vehicle walls or 12ft / 4 m tall wall segments used by the military to reinforce strategic points.
These are essentially portable fortifications. They are made of rebar and concrete and are exceedingly hard to destroy directly. Use cranes and heavy trucks to move them, as they weigh a few tons each.
Another important advantage defenders have is that the attackers have to come to them -- so there's not much need to carry supplies to the front line.
Pre-prepared ammo caches can be strewn throughout the city to keep defenders in the fight as long as possible. Urban landscapes offer a lot of hidden spots where ammo or weapons can be deposited discretely. Food, water, and medical supplies are also essential, so make sure these are distributed throughout the engagement zone as well.
Strongpoints should have designated rooms for storage of such supplies. Smaller items such as magazines or grenades can be distributed in smaller quantities throughout several points of the building, to ensure that soldiers always have what they need on hand.
Attacking an urban environment is a very daunting proposition even for the most well-trained of military forces. It gives defenders an ideal landscape to set up ambushes, entrench, deceive their attackers, and launch counter-offensives. Making the most of the terrain, and preparing carefully, can give defenders a huge upper hand against their foes while making it hard for attackers to leverage their strengths. such landscapes can level the playing field even against a superior attacking force. The events in Ukraine stand as a testament to this.