A soldier crouches in dry grass and a launch tube no longer than his arm coughs out a small missile. Before it has cleared the treeline its wings have snapped open and an electric motor has taken over. For the next quarter of an hour it will circle overhead, sending live video back to a hand-held screen, and it will only become a weapon when a human decides it should.

That is a loitering munition, popularly called a kamikaze drone: part reconnaissance drone, part missile, built to wait over a battlefield until a target appears and then dive onto it. Once a niche Israeli speciality, the category now ranges from 2.5 kg backpack rounds to 200 kg long-range attack drones launched by the hundred. Here is how they work, and why their labels cause so much argument.

Missile, Drone or Something in Between?

The easiest way to understand a loitering munition is to place it between two older ideas. A cruise missile is launched at a target that has already been found. It flies a planned route, often at low level, and has no reason to wait: the decision to strike was made before launch. A reusable armed drone such as the MQ-9 Reaper is the opposite. It searches for hours, fires a separate missile or bomb, and flies home to be refuelled.

A loitering munition merges the two. Like the Reaper, it can be sent to an area without a precise target and spend time searching. Like a missile, it carries its warhead inside its own airframe, so the aircraft and the weapon are one and the same. Once it attacks, it is gone. The US Congressional Research Service notes that the Department of Defense typically uses the term one-way attack UAV for a single-use aircraft with an integrated explosive warhead, and treats it as broadly the same family.

The trade-off is simple. Because the vehicle is expendable, it can be small, cheap and simple. Because it can wait, it does not need a target to be located in advance by another sensor. That makes it attractive against targets that appear briefly and move: an artillery piece that fires and relocates, a radar that switches on for a few minutes, a vehicle crossing open ground.

Launch, Transit, Loiter, Strike

Almost every loitering munition flies the same basic profile. It is launched, it transits to a search area, it loiters there while its sensor looks for a target, and it either dives onto that target or is called off. The details vary enormously by type, from a few kilometres and a few minutes for a backpack round to well over a thousand kilometres for the largest long-range designs.

Launch is where the family first divides. The small American Switchblades are fired from the same sealed tube they are carried in, using a small charge to push the round clear before the wings unfold. Israel’s Harop leaves a canister mounted on a truck or a ship. Russia’s Lancet is thrown into the air by a catapult. The heavy Shahed-136 needs a short-burn rocket booster to get airborne from a launch rack, such as a tilting truck-mounted container, as described by the CSIS Missile Defense Project.

Propulsion follows size. Small, short-range rounds almost always use an electric motor driving a propeller. It is quiet, starts instantly and gives off little heat, which makes the munition harder to hear or spot with a thermal camera. Long-range designs need more energy than any affordable battery can store, so they use small piston engines. The Shahed-136, according to CSIS, is powered by a roughly 50 hp two-stroke, four-cylinder engine derived from the German Limbach L550 design, which Iran produces as the MD550.

The Loiter: Sensors, Datalinks and a Human Decision

The loiter phase is what gives the category its name. Over the search area the munition flies orbits while a nose camera, often combined with a thermal imager, streams video back to the operator. On the Switchblade family that operator holds a ground control unit; on long-range systems the control station may be hundreds of kilometres away and the link may run through relays.

Who decides to attack is the central technical and ethical question. In a man-in-the-loop system the operator selects the target on the video feed and arms the warhead; software then guides the final dive. AeroVironment says a required man-in-the-loop arming sequence provides positive target confirmation on Switchblade. IAI says Harop is supervised by remote human-in-the-loop mission control and can be aborted if required.

At the other end of the scale sits autonomous target recognition. The IAI Harpy, the anti-radar ancestor of the Harop, is described by its maker as fully autonomous: it is launched into an area, listens for the emissions of enemy air-defence radars and homes on them without a human choosing each target. Russian developers have claimed that the Lancet can find and track targets using onboard software. US policy, set out in DoD Directive 3000.09 and updated in 2023, requires autonomous and semi-autonomous weapons to be designed so that commanders and operators can exercise appropriate levels of human judgement over the use of force.

Warheads, Wave-Offs and the Terminal Dive

Warheads scale with the airframe. The smallest rounds carry little more than a grenade-sized charge aimed at people or soft vehicles. Mid-size types such as the Switchblade 600 carry anti-armour warheads intended for light armoured vehicles. Long-range designs carry tens of kilograms of explosive: commonly cited figures are about 23 kg for the Harop and up to 50 kg for the Shahed-136.

The terminal dive is usually steep and fast, which shortens the time a defender has to react and lets a shaped-charge warhead strike the thinner top armour of a vehicle. What separates the better-designed systems is what happens if the operator changes their mind. AeroVironment markets a patented wave-off and recommit capability that lets an operator cancel an attack within seconds of impact, for example if civilians appear, and send the munition back up to search again.

Five Loitering Munitions, Five Design Philosophies

IAI Harpy and Harop. Israel Aerospace Industries describes the Harpy as the world’s first anti-radiation loitering munition, built to hunt air-defence radars. Its larger successor, the Harop, swaps the radar-homing seeker for an electro-optical and infrared camera and a human in the loop. IAI now quotes up to nine hours of endurance; defence publications have reported a range of about 1,000 km and a warhead of around 23 kg. Azerbaijan reportedly used Harops against Armenian forces, first in 2016 and on a larger scale in 2020.

AeroVironment Switchblade 300 and 600. The Switchblade 300 weighs 2.5 kg (5.5 lb), fits in a backpack and, in its original form, offered up to 15 minutes of flight and a 100 mph dash speed, according to AeroVironment. The anti-armour Switchblade 600 followed in 2020. AeroVironment quotes more than 40 minutes of endurance for it and, with control handed to a forward ground station, a reach of more than 90 km (55 miles). The United States began supplying both types to Ukraine in 2022.

ZALA Lancet. Unveiled by ZALA Aero, part of Russia’s Kalashnikov Group, at the Army-2019 forum, the Lancet-3 is a catapult-launched, electrically powered round of about 12 kg with a warhead of around 3 kg, about 40 minutes of endurance and a range of roughly 40 km, according to the manufacturer’s published figures. In Ukraine it has been used widely against artillery, air-defence systems and armour.

HESA Shahed-136. IL Shahed-136 is a different animal: a delta-wing aircraft of about 200 kg that cruises at around 180 to 185 km/h towards pre-programmed coordinates. Iran’s Revolutionary Guard has displayed figures of 2,500 km range and a 50 kg warhead; CSIS notes that other estimates of range run from 1,000 to 2,000 km. Russia produces it as the Geran-2 and has since fielded jet-powered derivatives.

Is the Shahed a Loitering Munition at All?

The Shahed-136 is routinely called a kamikaze drone or a loitering munition, but it does very little loitering. In most reported attacks it flies a pre-programmed route to fixed coordinates, such as a power station or a building, and dives onto them. There is no operator searching a video feed and no wave-off. That is why many governments and analysts prefer the term one-way attack drone, and why others argue it is simply a missile.

The argument matters for export controls, arms-control talks and air-defence planning, because each label implies different rules and different countermeasures. The missile specialist Fabian Hoffmann argues that under NATO’s broad definition of a missile, a self-propelled, guided munition, long-range attack drones such as the Shahed-136 and Geran-2 already qualify, and are best understood as cheap, slow relatives of the cruise missile.

In practice the categories blur. Some newer Russian Geran variants have reportedly been fitted with cameras and mesh-radio datalinks, giving them some of the in-flight control of a true loitering munition, while the largest loitering munitions such as Harop can be flown much like a long-range missile. The useful question is less what a weapon is called than whether it can search, whether a human confirms the target, and whether the attack can be called off.

How Loitering Munitions Are Countered

Defeating a loitering munition starts with finding it, and that is the hard part. Small electric rounds have tiny radar and thermal signatures and fly low and slow, close to the clutter of birds and terrain. Afterburner’s explainer on counter-drone systems covers the detect, track and defeat chain in detail.

Electronic warfare attacks the weak links. Jamming the control datalink can stop a man-in-the-loop munition from receiving its operator’s commands, and jamming or spoofing satellite navigation can degrade designs that rely on it, although many now combine satellite and inertial navigation for this reason. Against long-range one-way attack drones, Ukraine has relied on a layered mix of radar networks, anti-aircraft guns, mobile fire teams, fighter aircraft and, increasingly, cheap interceptor drones.

Physical protection has made a comeback as well. Metal cages and netting fitted over vehicles and artillery pieces aim to set off a small warhead before it reaches the armour. None of these measures is complete on its own, which is why the cost exchange between cheap munitions and the defences needed to stop them has become one of the defining problems of modern air defence.

Sources: AeroVironment, Israel Aerospace Industries, ZALA Aero / Kalashnikov Group via Army Recognition, CSIS Missile Defense Project, Janes, Congressional Research Service, US Department of Defense, Defense News, The War Zone, Airforce Technology, Army Technology, Kyiv Post, Missile Matters (Fabian Hoffmann).

Header photo: U.S. Marine Corps photo by Cpl. Jennessa Davey, public domain, via Wikimedia Commons