It is a military axiom that whatever new technology comes along, the “ Poor Bloody Infantry ” still need to take and hold ground. Even in the drone-saturated battlefields of Ukraine where drone-on-drone combat is increasingly common, human fighters are a crucial element.

However, the rules are subtly shifting. Before, there was literally no alternative to sending foot soldiers in first to buildings and trenches. Now the situation has altered. Soldiers still go in, but an increasing number of videos from Ukraine show the drones going in first.

Piloting an FPV around the inside of a building, as in the famous 2021 “Bowling Alley” video , may be routine in the movie world, but in the war zone in 2022 it was a stunt for elite pilots only. Now increasing numbers of videos show FPVs searching through buildings and trenches and locating and engaging the enemy.

Two things are obvious. One is that tactics from the pre-drone age need to be updated fast for the new reality. The other is that drones are carrying out operations with progressively fewer humans in the front line and the trend will continue.

The Eternal Challenge Of Urban Conflict

Even as technology transformed warfare in the early 20 th century it was accepted wisdom that everything still came down to the foot soldier. Progressively more capable airpower, tanks and even nuclear weapons did not change this basic truth. As British WWII commander Field-Marshal Wavell wrote in his 1948 essay In Praise of Infantry 1948 , “ All battles and all wars are won in the end by the infantryman .”

T.R. Fehrenbach put it more forcefully in his 1963 book “This Kind of War” -- "You may bomb it, atomize it, pulverize it and wipe it clean of life—but if you desire to defend it, protect it, and keep it for civilization, you must do this on the ground, the way the Roman legions did, by putting your young men in the mud ."

Even 1950s techno-optimist science fiction doubted whether technology would ever change things. The infantryman protagonist of Robert Heinlein’s 1959 classic Starship Troopers does not think he can be replaced: “ Maybe they’ll be able to do without us someday. Maybe some mad genius…will devise a weapon that can go down a hole, pick out the opposition, and force it to surrender or die — without killing that gang of your own people they’ve got imprisoned down there. ”

This view is embedded in current training manuals . While it may be possible to reduce urban strongholds with heavy artillery or aircraft, taking a town rather than destroying it is a job for foot soldiers. The Eight Rules of Urban Warfare and Why We Must Work to Change Them written by John Spender for the Modern War Institute in 2021, reiterates the challenges of fighting in dense urban environments, drawing on the Battle of Mosul in 2017.

Briefly,Spender notes that urban environments provide abundant hard cover, giving the defender concealment and protection from even heavy weapons. Reconnaissance and surveillance literally run into a brick wall. Attackers are visible and vulnerable as they approach, while defenders typically maintain freedom of movement by creating routes through and under buildings, going underground when needed.

The three-dimensional battlefield is difficult to control, with many blind spots and an opponent who may be able to concentrate firepower at will. Fighting tends to be at very close range, negating much of the advantage of a technologically superior force.

Seen from this viewpoint, taking an urban area is not much changed from WW2 or even WW1.

When drones come into play, the situation changes radically.

Made For Three-Dimensional Warfare

In a typical video from Ukraine a drone enters through a window and passes through three rooms before finding a Russian hiding in a damaged closet. Another shows a hunt for Russians moving around inside a damaged building . A third shows how one searches a building and tracks down a Russian who entered previously.

These operations are not confined to small buildings. One sped up video shows an FPV searching through a large apartment block .

The advance on an enemy-held block, hazardous to foot soldiers, is not a problem for drones. Small and agile, flying at 40 mph or more, they are extremely difficult targets for small arms fire even at low altitude. And if an opponent does opt to shoot at an incoming FPV, they make their location visible to other drones.

Navigating in three dimensions is tough for infantry, especially when defenders have destroyed or booby-trapped the stairwells and are shooting from above. Drones do not need stairs or ladders, and the sixteenth floor is as accessible as ground level.

Drones do not have the same situational awareness as foot soldiers, and the continuous buzzing of their rotors gives away their position. They may be easy to locate, especially inside buildings where the operator has to maneuver carefully and rotate the drone to get a 360-degree view of the room. But life expectancy of an FPV is exactly one flight. When one gets destroyed the operator is ready with the next. Drone casualties are not a problem.

Signal loss can be an issue, as low-powered radios may lose touch in a dense urban environment. This has not been solved. In Ukraine, the main solution is fiber-optic drones, which are more than maneuverable enough to handle indoor spaces. In Gaza and elsewhere, some drone operators use mesh radio, where each drone acts as a node in the network, so they only need to connect to the nearest drone and not all the way back to the operator.

Xtend, whose drones are used extensively in Gaza, note that their drones are used to clear out tunnels. In the civilian world, drones map out dangerous mine workings beyond the each of radio.

Some of Xtend’s drones for indoor operations have shrouded rotors which are easier to use in enclosed spaces, as they can bounce off walls and other obstacles rather than breaking a rotor blade. Russian sources claim that Ukraine is using similar “ Tiny Whoop ” drones for urban operations. In some cases the rotor blades are visible, suggesting conventional FPVs are being shown with unusual skill. with considerable skill rather than special drones . In other cases , the lack of visible rotors and the presence of a “fisheye” wide angle lens suggests that there are special drones for infiltrating buildings.

Looking ahead, the surveying technique of Simultaneous Location And Mapping (SLAM) allows a sensor-equipped drone to build up a complete 3D model of its environment as it goes. Applied to military operations this would allow commanders to map out every cubic inch of space in a building and spot where there are hidden rooms or areas which have not been cleared.

Precision And Discrimination

FPVs are capable of entering buildings and engaging enemy fighters. Even small drones can carry powerful warheads. In one example an FPV operator locates a Russian inside a cottage, and the blast seen from outside demolishes the entire structure.

If that was all they could do, FPVs would only be another version of heavy artillery or air power destroying targets in cover. As Heinlein notes, the challenge is killing selectively, forcing the enemy to surrender without harming bystanders.

FPV operators can take surrender and many examples have been redorded. In one , reported by Ukrainian military news source Militanyi , a drone operator of the 31 st Brigade located a Russian inside a building injured by a previous drone strike who wished the surrender. Instead of striking, the drone led him out to captivity. There are videos of similar incidents on X.

FPVs can hit captors while sparing captives. In a rescue mission in March, the Morok ("Darkness") assault group of Ukraine's 225th Separate Assault Regiment freed two PoWs by hitting their guards with FPVs.

This gets close to Heinlein’s requirement for “ a weapon that can go down a hole, pick out the opposition, and force it to surrender or die— without killing that gang of your own people they’ve got imprisoned down there” which he thought would still be impossible in the 23rd century.

The obvious counter to drones is plenty of wire mesh or netting, and trenches are now invariably covered to prevent drone entry. Trench systems have frequent weighted net or bead curtains to prevent drones moving freely. Fighting positions in urban areas will need similar protection. Interior doors, if intact, will also stop the first drone.

However, even in WWII, urban combat featured extensive use of “ mouseholing ,” getting around by means of holes in walls to avoid areas covered by enemy fire. Mouseholes are typically around 24” in diameter, in contrast to full breaches which are more like 36” across and 50” high. Mouseholes are created by small explosive charges weighing a few pounds which can easily be carried by FPVs.

Drone operators already use a lead FPV to blast a hole in a wall or window which a second drone flies through, a tactic seen in this video. Many videos from China show this tactic being used with kinetic lead drones to break glass windows .

Specialized breaching drones and accumulated expertise from Ukraine should produce a battle manual on drone urban mobility. Expect FPVs to bypass obstacles to gain access throughout buildings.

Urban combat requires a lot of ammunition – up to four times as much as rural operations -- and FPV-led operations will require a significant stockpile of drones. But if these are available, any urban area may, in principle, be searched and cleared before the first soldier sets foot in it.

This is still uncharted territory. Drone warfare is still evolving. But already we are at a stage where it makes little sense to send a human in until the drones have done everything they can to ensure that an objective, whether it is a trench or a city block, is thoroughly clear of hostiles. Anything that involves sensing squads of infantry to close with enemy positions invites needless casualties.