Active electronically scanned array (AESA)
Advanced radars that have been developed to upgrade the capabilities of fourth-generation fighter jets. A computer can steer the radio beam without physically moving the antenna. Among their advantages is that they are harder for enemies to jam and are also more difficult for a hostile radar to intercept and thus pinpoint the position of its target. They can also perform a wide variety of tasks, such as monitoring objects in the air, on land and on water, which is known as multimode capability.
A surprise attack conducted by an enemy lying in wait.
Anti-personnel landmine
See Landmines.
Anti-tank weapons
Portable rocket launchers that can penetrate the thick armour of tanks. America’s Javelin, one high-tech model, has infrared seekers which can lock onto and pursue a moving target up to 2.5km away. Troops can “fire-and-forget”, meaning they can take cover quickly after launching. The 8.4kg warhead dives on its target, allowing it to penetrate the thinner armour on top of a tank’s turret. Other models include the British-Swedish Next Generation Light Anti-tank Weapon (NLAW). For more, read our Explainers on Ukraine’s anti-tank missiles and its supply from the West.
Armoured personnel carriers (APC)
Vehicles used to transport small groups of troops (usually around 12 including the vehicle’s crew) in combat. They are armoured to offer protection against enemy fire, improvised explosive devices and mines. Some models move on tracks, though modern versions commonly have eight untracked wheels. Most are armed with a machinegun or a small cannon.
Artillery weapons employ indirect fire, meaning their targets can be out of sight—even tens of miles away. Artillery spans everything from compact mortars to 30-tonne guns on tracks capable of raining devastating fire onto large areas. This firepower can pin down enemy forces or destroy them, often to allow infantry and armoured vehicles to advance. Artillery can also be used to counter other artillery (see counter-battery fire). For more, read our article about the vital role of artillery in Ukraine.
Asymmetric warfare
A conflict in which the sides are unmatched in terms of military strength and capability. This could involve a large military power’s army versus that of a smaller one (think Ukraine versus Russia), or when a conventional military force faces an insurgency that uses unconventional methods and equipment, such as terrorist attacks or improvised explosive devices, to exploit their more powerful opponent’s weaknesses.
Attritional warfare
A military strategy that aims to wear down an enemy force by systematically destroying its troops, weaponry and other equipment using firepower. It is often portrayed as the opposite of manoeuvre warfare.
Autonomous weapons
The definition of an autonomous weapon is highly contested. Many consider it to be any weapon capable of unleashing lethal force without direct human command. That can range from thinking machines capable of deciding when and how to fight, to a missile that can select among several targets in a defined area after being fired. Countries have not agreed on when a weapon becomes fully autonomous. For the implications of military robotics on the laws of war, read our Briefing or our Special Report on the future of war.

Ballistic missile
A missile propelled by a rocket for only the first stage of their flight, before it descends unpowered towards its target. Their trajectory has a characteristic arch shape that contrasts with the straight-line flight of a cruise missile. Ranges vary. Intercontinental Ballistic Missiles (ICBM), the class with the farthest reach, have a range of more than 5,500km, according to arms-control treaties.
A military unit containing up to 1,000 soldiers. Battalions are made up of several companies and are generally led by a lieutenant colonel. A battalion with other capabilities attached is sometimes called a battlegroup.
Biological weapons
These munitions involve the use of living organisms, or the toxins such organisms produce, to do harm. Examples include the weaponisation of infectious pathogens, such as anthrax or smallpox. Even small amounts can be very dangerous. For instance, models suggest a kilogram of anthrax, dropped on a city, could kill 100,000 people. The UN’s Biological Weapons Convention bans the weapons’ development and use, but international oversight is weak. For more, read our Explainer.
A military unit that comprises up to 5,000 soldiers, depending on the army. Brigades are made up of several battalions, generally of different types, be they infantry, artillery or support. In the American military they can be led by a colonel, but in the British military a major-general or brigadier takes command. Brigades were the main combat unit in America’s army in the 2000s and 2010s.
A senior army-officer rank that sits above a colonel but below a major-general. The rank is referred to as a brigadier-general in America.

In the American and British armies captain is a commissioned-officer rank, above a lieutenant and below a major. A captain would normally lead a company. In these countries’ navies, however, captain is a higher rank, equivalent to an army colonel.
Chemical weapons
These munitions use toxic chemicals to harm an enemy. Examples include Novichok, a nerve agent used by Russia in 2018 to poison Sergei Skripal, a former GRU officer who spied for Britain. Unpredictable in their effects, they are not terribly effective as military instruments. They are also illegal under the Chemical Weapons Convention. Not to be confused with biological weapons. For more read, our Explainer.
Close-air support aircraft (CAS aircraft)
Aircraft that support ground troops and fire upon battlefield targets as they appear, rather than carrying out pre-planned bombing raids. Russia’s Su-25 Frogfoot is an example: it is designed to fly low and slow, striking ground targets with cannons, rockets and missiles. For more, read our Explainer on how badly these old-fashioned, ground-attack aircraft have fared in Ukraine where air-defences are thick.
Cluster munitions
Warheads that scatter grenade-sized “bomblets” over a large area, cancelling out aiming errors. They can be devastating against massed infantry. Human-rights organisations say that their use in populated areas is a violation of international law, because bomblets often fail to detonate, leaving a deadly trail of unexploded munitions. For more, read our Explainer.
A rank of commissioned officer in the army that sits above a lieutenant colonel but below a brigadier.
Combined arms
An exercise or operation that brings together different military branches, be it infantry, artillery, engineers, or other specialists. Each branch compensates for the weaknesses of the other: tanks are well armed and protected, for instance, but need dismounted infantry and artillery to suppress enemy anti-tank teams nearby.
Command and control
The structures and principles through which senior officers exercise authority over their forces and approach decision making. Modern armed forces tend to favour mission command, in which soldiers on the ground are empowered to follow their initiative in line with the commander’s intent.
Command, control, communications, computers, intelligence, surveillance and reconnaissance (C4ISR)
The combination of capabilities that provide commanders with the ability to see through the “fog of war”, providing situational awareness, an understanding of what the enemy is doing or planning to do, and shortening the “kill chain” (the process required to locate and then attack a target). A C4ISR system gathers information from all parts of the battlefield using information from satellites to aircraft and intelligence gathered by soldiers on the ground. It then uses computing power to process the information and display it, and secure communications to issue commands and get relevant information to forces in the field.
Commissioned officer
Senior officers within the armed forces, who have received their rank by a “commission” from the head of the military, i.e. the monarch in Britain or the president in America. In practice, that means they have been specially trained for leadership.
A military unit made up of at least three platoons and generally led by a captain or a major. The size and structure of a company can differ between armies, but they tend to contain no more than 250 soldiers.
A rank of non-commissioned officer in the army.
A military unit usually comprising around three divisions, though they can be larger—in America’s military corps can contain up to 45,000 soldiers. They are normally commanded by a lieutenant general, and are the largest unit of organisation employed in combat. A corps typically fights the deep battle, such as delivering cyber effects well behind the front lines, as opposed to the close battle, at the front lines.
Counter-battery fire
A way of using artillery to counter artillery. Radar works out the trajectory and thus the likely origin of incoming shells. The coordinates are immediately sent to friendly guns, which fire back at the source. See also counter-battery radar.
Counter-battery radar
Trailer-mounted systems that work out where incoming artillery shells were fired from. One such system that Russia is using against Ukraine, the Zoopark-1m, can simultaneously pinpoint the origins of a dozen incoming 155mm shells from at least 12km away. COBRA, a European-made counter-battery radar, can do likewise for as many as 40 artillery pieces roughly 100km away. The radars help direct retaliatory attacks against enemy artillery, known as counter-battery fire.
The measures a government takes to defeat an insurgency. As well as military means, effective counterinsurgency, or COIN, also relies on softer social and political tools to stop insurgent groups gaining popular support.
Cruise missile
Missiles propelled by jet engines, allowing them to fly within the atmosphere at relatively low altitudes. They often navigate using positioning and navigation systems such as America’s GPS to find their way to their targets.
The targeting of computer networks, computer information systems and other electronic infrastructure in order to cause harm to another country. Experts often distinguish computer network exploitation (essentially, hacking) from computer network attack (such as the deletion of data). But cyberwarfare is often intended to have a psychological effect. We considered the rules for responsible cyber warfare (in 2023).

Deep battle
If the “close battle” is the front line where troops clash directly, the deep battle—an idea developed by Russian military theorists in the 1930s—is about attacking enemy forces well to the rear, particularly targets like command and control hubs, logistics, ammunition depots and barracks. Ukrainian attacks on Russia using HIMARS and Storm Shadow cruise missiles are part of the deep battle. The deep battle is often part of shaping operations.
Demilitarised zone (DMZ)
An area that opposing powers agree not to use for military purposes. Weapons and other military equipment are usually banned to allow a safe space for diplomatic negotiations or visiting civilian politicians. In practice, DMZs don’t always entirely live up to their name: the zone between North and South Korea, for instance, was at one stage home to two million landmines.
Depleted uranium shells
Munitions made from depleted uranium, a by-product of enriching the element which is necessary for atomic energy or nuclear bombs. Depleted uranium is less radioactive, as it contains a lower proportion of the fissile uranium 235 isotope. It makes excellent ammunition because it is dense, prone to self-immolate on impact, and sharpens as it bores through armour.
Direct fire
When a weapon, such as a rifle or a tank’s gun, is aimed at a target in the user’s line of sight. The opposite of indirect fire.
A large military unit that usually contains between 10,000 and 15,000 soldiers. They are generally led by a major-general. Divisions can operate autonomously in the field, with self-contained logistics, reconnaissance and artillery support. America’s army is increasingly shifting its focus from the brigade, which was an independent combat formation for much of the war on terror, to the division, which are needed to manage larger-scale fighting.
The set of core principles that underpins an armed force’s actions as it pursues its country’s strategic objectives. For instance, our Explainer from 2017 outlines the details of India’s “Cold Start” military doctrine, a limited-war strategy designed to seize Pakistani territory swiftly without, in theory, risking a nuclear conflict.
Close-range combat between two aerial opponents. At the start of the first world war this involved two pilots duelling with pistols. By the end of the cold war, beyond-visual-range missiles had made dogfighting a rarity. Today unmanned drones sometimes ram into each other in the skies above Ukraine. For more about those drone dogfights and the future of aerial warfare, read our Explainer.
A craft without a human pilot onboard. Drones are commonly thought of as airborne devices, but some operate on water (see naval drone). The airborne variety are technically referred to as uncrewed aerial vehicles (UAVs). They are either controlled remotely from the ground or by an onboard autopilot (known as “autonomous drones”). Small commercial drones are typically used for reconnaissance, feeding video footage back. So-called loitering munitions (or “kamikaze drones”) can hover over an area for longer periods before identifying a target and crashing into it. Meanwhile, strike drones, like America’s Reaper or the Turkish TB2, can carry and deliver bombs and missiles over hundreds or even thousands of kilometres. For more, read our articles on the uses of strikes drones in Ukraine, or on the ways that commercial drones have been repurposed for military use. You can also read our Explainers on Russia’s use of “kamikaze” drones and on how UAVs dogfight over Ukrainian skies.

Electronic warfare (EW)
The battle to control, influence or disrupt the electromagnetic spectrum in war. That can include locating an enemy by their radio emissions, jamming their communications or disrupting their radar. For more, read our Explainer (from 2022) on the battle to jam drones in Ukraine, or our article (from 2023) on Russia’s evolving electronic-warfare tactics.
Expeditionary Force
In its broadest definition, a group of soldiers deployed in a foreign country to carry out a specific objective. But modern expeditionary forces generally have more precise characteristics. They tend to be small in size and able to conduct missions at long distances while separated from conventional logistics.

Fifth-generation fighter jets
The most advanced currently operational fighters, characterised by their incorporation of stealth technologies. The most ubiquitous is the F-35, which will be the mainstay of American and allied air forces into the middle of the century. The term comes from succeeding generations of fighters. The first generation included the F-86 Sabre and the MiG15, which fought each other in the Korean War. Second-generation fighters included the supersonic but ill-fated F-104 Starfighter and the MiG21. The most successful third-generation fighter was the F-4 Phantom. Fourth generation fighters include the F-16, the F-15 and the MiG-29. So-called 4.5-generation fighters, such as the Typhoon, are upgraded fourth generation fighters with features such as AESA radar.
The quantity, size and type of munitions that an armed force is able to deploy against an enemy. Armed forces sometimes use the term “lethality”.
Small metal projectiles released from a bomb or artillery-round to indiscriminately pepper an area. Apart from fending off attacks at short range, flechettes have few advantages over similar munitions. Their footprint is that of a wide cone, not the 360 degree spread of a shell. And they cost much more to produce than fragmenting rounds. They produce disproportionately severe injuries. For more, read our Explainer.
Fog of war
Uncertainty derived from the fast-moving and unpredictable nature of combat. Such ambiguity can affect the situational awareness of soldiers, commanders and whole armies, limiting their understanding of what the enemy is doing or planning to do.
Four-star general
See general.

GMLRS (Guided Multiple Launch Rocket Systems)
GPS (Global Positioning System)
An American navigation system that uses satellite signals to accurately pinpoint locations. This is one among several types of Global Navigation Satellite Systems (GNSS), such as Russia’s GLONASS or China’s BeiDou. The receiver picks up precise time signals from several satellites and calculates its position by triangulation. GPS-guided munitions have almost completely replaced unguided bombs in America’s arsenal. The technology is expensive but almost guarantees a hit, assuming the target is stationary and its location is known. For more, read our Explainer.
A way of rendering an enemy’s Global Positioning System (GPS) useless. GPS satellites are around 20,000km from Earth, but their transmitters are no more powerful than a car’s headlight. Their weak signals can sometimes be drowned out, or “jammed”, by radio transmitters operating on the same wavelength. For more, read our Explainer.
Normally the highest rank of officer in an army. America’s army technically has the higher rank of “General of the Army” but it is only awarded at wartime, when the general in command needs to be of equal or higher rank to those of other nations’ armies.
Guerilla warfare
Fighting carried out by lightly armoured groups of troops, typically against more powerful militaries. Guerilla warfare is the stuff of insurgency: it involves fast-moving fighters who are skilled at operating in difficult terrain and effective at conducting operations like ambushes.

HARM (High-speed Anti-Radiation Missiles)
Launched from an aircraft, these American missiles home-in on and destroy air-defence radar. They have a range of some 145 km and are able to locate radar systems even after they have been turned off. Even if not fired, the threat these air-to-surface missiles pose can force radar operators to turn off their sets and lie low. For more, read our Explainer.
HIMARS (High Mobility Artillery Rocket System)
An American lorry-mounted rocket launcher that fires different types of shells directed by rocket engines. These satellite-guided missiles are more accurate over long distances than standard munitions and allow a three-man HIMARS crew to launch a salvo and then drive away immediately, making it hard for enemy artillery to return fire. America has given Ukraine HIMARS loaded with GMLRS, a short-range rocket that carries a 91kg warhead and can consistently hit targets up to 70km away; but, if loaded with longer-range ATACMS missiles, a HIMARS can strike up to 300km away.
An artillery piece that is designed to fire shells in a shallow arc over long distances. Usually more precise than a cannon and with longer range than a mortar.
Human intelligence (HUMINT)
The gathering of information about another power through contact with people, i.e., by recruiting agents in areas of enemy control. For more, see our recommendations on what to read to understand intelligence and espionage.
Hybrid war
A conflict in which a combatant mixes lots of different kinds of fighting. Initially popularised by Frank Hoffman, a defence scholar, its meaning has since loosened. The term increasingly refers to the employment of non-lethal forms of attack and subversion, such as cyber-attacks or election meddling. For more, read our Explainer.
Hypersonic boost-glide weapons
See Hypersonic weapons.
Hypersonic cruise missiles
See Hypersonic weapons.
Hypersonic weapons
Missiles that travel more than five times the speed of sound, or around 1.6km per second. Crucially, they can sustain those speeds at lower altitudes than long-range ballistic missiles, which reach similar velocities as they re-enter the atmosphere. Hypersonic missiles come in two types. Hypersonic cruise missiles are powered by rockets or jets throughout their flight. Hypersonic boost-glide weapons are launched into the upper atmosphere atop ballistic missiles, but then release unpowered hypersonic glide vehicles (HGVs) which fly lower, faster and less predictably than old-fashioned re-entry vehicles. For more, read our Explainer.

Improvised explosive device (IED)
Homemade bombs generally constructed from chemicals used in agriculture and industry. IEDs can often be detonated remotely via radio or phone signal. They are associated with attacks led by insurgencies or other non-conventional forces.
Indirect fire
When a weapon is aimed at a target not visible to the person controlling it, usually employed by artillery. For more, read our article about the importance of artillery fire in Ukraine.
Infantry fighting vehicle (IFV)
Lighter than main battle tanks but with more weapons than armoured personnel carriers, IFVs offer moderate protection to crews and infantry while carrying substantial guns. For example, America’s Bradley vehicles have enough firepower to destroy many tanks. IFVs give armed forces manoeuvrability on the battlefield and are used to penetrate enemy lines. For more, read our article about the West’s deliveries of IFVs to Ukraine.
A sustained rebellion against a recognised authority, such as a national government or occupying force, by an armed military-political group. Insurgencies often engage in guerilla warfare or other forms of irregular attack. Insurgency differs from terrorism because the groups involved aim to gain political control, rather than carry out indiscriminate violence.
Intercontinental Ballistic Missiles (ICBM)
A class of ballistic missiles with a range of more than 5,500km. They are typically associated with nuclear weapons.

See Anti-tank weapons

Kamikaze drone
See loitering munitions.
Kill chain
The kill chain refers to the process of identifying a target, making a decision over whether and how to attack it, and then attacking it using an “effector”, which can include a lethal weapon or a non-lethal tool such as an electronic jammer. America’s armed forces use the acronym F2T2EA: find, fix, track, target, engage and assess. Armed forces generally want to shorten the kill chain, to give targets less time to get away and to paralyse an enemy. The term “kill web” is sometimes used.

Explosive devices on or hidden under the ground that detonate when a person steps on or near them or a vehicle travels over them. Minefields can force an enemy to turn, which exposes their flank and makes them especially vulnerable. They can also be used to “canalise” the enemy, channelling attackers into unfavourable terrain, where they may be more exposed to concentrated artillery fire. The use of anti-personnel mines—those designed to target people—is banned by the Ottawa treaty of 1997. Yet America, China and Russia are not among the treaty’s signatories. And mines designed to destroy vehicles such as tanks are still allowed. Read our Explainer on the use of anti-tank mines in Ukraine.
In the army a lieutenant (or first lieutenant in the American army) is a junior commissioned officer, above a second lieutenant but below a captain. In the navy, however, lieutenant is a higher rank, equivalent to an army captain.
Lieutenant colonel
An army-officer rank that sits above a major but below a colonel. A lieutenant colonel would typically command a battalion.
Lieutenant general
A senior army-officer rank that sits above a major general but below a general.
An old-fashioned tactic for firing unguided rockets from an aircraft. Rather than launch the missiles in pairs directly at a target on a downward angle, the pilot flies low before climbing and firing an entire pod of rockets steeply upwards, after which the pilot veers away. The technique, also known as “tossing”, was developed in the 1940s and is now rarely used if guided missiles are available. For more, read our Explainer.
The process of moving personnel, equipment and other military supplies from one place to another, and of maintaining said equipment.
Loitering munitions
Somewhere between a drone and a missile. These weapons, also known as “kamikaze” or “suicide” drones, hover over an area, potentially for long periods, before selecting a target and detonating on impact. Take America’s Switchblade—fired from a tube, the missile has wings that flip out after launch and an electric propeller that drives it forward. The operator can control it via an optical camera and an infrared thermal-imager on board. When the operator locks on to a target, the drone accelerates towards it, chasing it automatically if it takes evasive action. For more, read our article.

MANPADS (Man-portable Air Defence Systems)
A type of portable, anti-aircraft missile often fired from the shoulder. Typified by the heat-seeking American Stinger, MANPADS are generally effective against low-aircraft and at a range of a few kilometres. For more, read our Explainer.
MLRS (Multiple Launch Rocket Systems)
A rocket-launcher system, often armoured and self-propelled, that fires surface-to-surface missiles, mounted on the chassis of an armoured vehicle, such as America’s Bradley. The NATO-standard M270 MLRS carries two pods, with a total of 12 missiles. Later versions could fire precision-guided shells known as Guided Multiple Launch Rocket Systems (GMLRS), guided by satellite. For more, read our article about America’s advanced-missile deliveries to Ukraine.
Main battle tank (MBTs)
Heavily armed and armoured tanks such as America’s Abrams and Germany’s Leopard. Unlike light tanks, which tend to be cheaper and less well-equipped, MBTs can weigh around 70 tonnes and sprout large turret-mounted guns with several attached machineguns. Light tanks were more popular than MBTs during the cold war. But, as anti-tank guided missiles and armed drones became more effective, better-protected tanks replaced lighter models. For more, read our Explainers on the definition of a tank and the features of Germany’s Leopard 2 model, and our interactive on the future of the tank.
A rank of commissioned officer in the army, above a captain but below a lieutenant colonel. Major is also an officer rank in America’s air force (equivalent to its level in the army).
Major general
A senior army-officer rank that sits above a brigadier but below a lieutenant general. A major general leads a division, which contains between 10,000 and 15,000 soldiers.
In combat, manoeuvres denote the tactical movement of armour or troops to gain an advantage over an enemy. The term is also used to describe military training exercises, typically involving the shifting of soldiers or equipment across a large area.
Manoeuvre warfare
A military strategy that emphasises rapid movement to disrupt an enemy’s cohesion and will to fight. In contrast with attritional warfare, which gradually seeks to wear down an enemy through the systematic destruction of its troops and weaponry, manoeuvre warfare favours tactics like encirclement or unexpected attacks on an enemy’s rear or flank.
Soldiers not part of any country’s army who offer their services for pay. In the second half of the 20th century unstable parts of Africa and the Middle East, for example, were plagued by fighters–and private military companies–willing to be hired by the highest bidder. Some mercenaries are closely linked to states. For example, the Wagner Group, from Russia, fights in Ukraine and elsewhere. Read our explainer on the Wagner Group and a profile of its founder, Yevgeny Prigozhin.
A group of fighters that is not part of a regular army. Militias can serve governments, though they often represent the interests of an insurgency or other non-state actors.
An area of land or sea planted with mines. The Korean peninsula’s demilitarised zone is a famous example, at one point home to two million landmines.
Explosive devices that are placed on or hidden under a surface, be it the ground (landmines) or the sea (naval mines). The static bombs detonate when a person, vehicle or vessel comes into contact with, or sometimes simply approach, them.
Mission command
A style of military management that gives agency to rank-and-file soldiers. Commanders issue the principles and objectives of a mission and delegate responsibility for achieving it to more junior officers, allowing them to exercise their own initiative and judgment. Forces with mission command can be creative, altering tactics and seizing opportunities that arise. For more, read our Explainer and our article about the importance of the concept for America’s military strategy.
Mission creep
The gradual growth of an operation’s objectives beyond its initial goals. Mission creep is generally a bad sign, associated with foreign interventions gone awry.
A light artillery piece designed to hit its target by arcing the shot high in the air, so that the shell lands on its target from above (unlike a heavier cannon or a howitzer).

NLAW (Next Generation Light Anti-Tank Weapon)
See Anti-tank weapons.
Naval drone
Maritime vessels that operate without a crew. So-called “uncrewed surface vessels” (USVs) travel on the water’s surface, while “unmanned underwater vehicles” (UUVs, or “submarine” drones) are submersible and travel beneath the surface. Naval drones can be used for reconnaissance and, increasingly, combat. For more, read our article (from 2022) about the use of naval drones in Ukraine.
Naval mines
Static bombs that are deployed at sea and are designed to detonate when a vessel approaches or touches them. Drifting mines float on the sea’s surface; anchor mines are tethered to the seabed and lurk beneath the waves; and deepwater mines sink to the seafloor. The latter can pack in extra explosives because of their lack of buoyancy. For more, read our article on the importance of mines for naval strategy.
Nerve agent
A chemical that disrupts the messages sent from nerves to other parts of the body, causing paralysis and the loss of bodily functions. Examples included Novichok and Sarin. See also chemical weapons.
No-fly zone
When a country, or countries, prevents another from using warplanes to attack military targets or civilians on the ground over a given area. Simply declaring these zones is not enough. The power that commands it has to patrol the area with its own planes, suppress enemy air-defence systems on the ground and be prepared to fire at enemy aircraft. For more, read our Explainer.
No-man’s land
An area between two opposing military forces where neither commands control.
Non-commissioned officers
Enlisted soldiers who have risen through the ranks to take up lower-level leadership or specialist positions within their unit.
Non-strategic nuclear weapons
See Tactical nuclear weapons.

One-star general
See brigadier.
Open-source intelligence (OSINT)
The gathering of information through publicly available sources such as commercial satellite imagery, social media, or websites tracking shipping and aircraft activity. Commonly used by journalists and researchers to track military movements. For more, read our cover article and briefing from 2021, which explored OSINT’s emergence. You can also read our interactive article about the role OSINT is playing in Ukraine. And you can listen to our science podcast on the same subject.

A small military unit generally containing no more than a few dozen troops. Platoons are usually led by a lieutenant.
Porcupine defence strategy
A type of asymmetrical warfare. At its heart is a recognition that a smaller power needs to adopt nimbler and lighter ways of fending off a stronger enemy. Think David versus Goliath—or Taiwan versus China. Instead of buying expensive conventional equipment such as tanks, battleships and submarines—which are hard to hide and easy to strike with a missile—a “porcupine” strategist would focus on agile and concealable weapons such as portable anti-tank or anti-aircraft missiles. For more, read our Explainer about Taiwan’s porcupine defence.
Private military company (PMC)
A business that sells military services for profit. That can include specialist help with logistics and planning—or the provision of mercenaries. For instance, the Wagner group, a Russian mercenary outfit, calls itself a PMC. For more on Wagner, read our Explainer.

Shipping lanes intended to allow safe passage for vessels through mined, or potentially mined, waters.
In the army quartermasters are responsible for supervising barracks and distributing supplies like food or clothing. In the navy they are the officers responsible for navigation.

Systems that use radio waves to locate and track objects like aircraft, ships or missiles. Radar-guided munitions incorporate the technology to home in on targets with precision. Newer radars use active electronically scanned arrays (AESA) rather than mechanical antennae.
Scoping of an area to gather information about an enemy or terrain. Reconnaissance is carried out by a small group of soldiers, aircraft, satellite or, increasingly, drones. Typically, reconnaissance is to obtain specific information whereas surveillance is to monitor something more persistently.

SSBNs (Submersible Ship Ballistic Nuclear)
Nuclear-powered submarines that carry ballistic missiles that typically include nuclear warheads. South Korea is the only non-nuclear armed country in the world to operate SSBNs—its subs are armed with conventional ballistic missiles.
SSNs (Submersible Ship Nuclear)
Nuclear-powered submarines that carry conventional, non-nuclear weapons like cruise missiles.
Scorched earth
A strategy in which an army destroys infrastructure and other amenities that could support an enemy force, including buildings, crops and livestock. The term is often associated with retreating armies that want to slow down an approaching enemy. But the policy can also be implemented by an advancing force that wants to entirely destroy an enemy’s military and civil infrastructure.
Second Lieutenant
The lowest rank of commissioned officer in the army.
A rank of non-commissioned officer in the army.
Shaping operations
Preliminary attacks intended to soften up and influence enemy defences before an offensive.
A projectile, usually a metal container shaped like a large bullet, which is filled with explosive or other incendiary material. Shells are commonly fired from artillery weapons.
Signals intelligence (SIGINT)
Information gleaned by intercepting and often deciphering enemy messages, be they from communication systems or other devices such as radar. This is the specialty of America’s National Security Agency (NSA) or Britain’s Government Communications Headquarters (GCHQ). Even if signals cannot be decrypted, they might provide information on the location of enemy forces or, if there is a burst of activity, on their status—the latter is called traffic analysis. For more, see our recommendations on what to read to understand intelligence and espionage.
Stealth technology
A suite of technologies that can help aircraft, missiles, ships and submarines avoid detection. Stealth aircraft have modifications to the fuselage, wing design and paint that reduce radar reflections. An early stealth aircraft was Lockheed’s F-117. Boeing’s B2 bomber, which looks like a flying wing, is another example. All so-called fifth-generation fighter jets, such as the Lockheed F-35, incorporate stealth technologies to enable them to operate in heavily contested airspace. Many cruise missiles, including Storm Shadow, incorporate stealth features too.
Strategic nuclear weapons
Large-yield nuclear weapons, usually mounted on ocean-crossing intercontinental ballistic missiles. Strategic nukes typically have yields measured in the hundreds of kilotons: their blasts are equivalent to letting off hundreds of thousands of tonnes of high explosive. In contrast with smaller tactical nuclear weapons, strategic missiles are the city-destroying weapons of all-out nuclear exchange. For more, read our Briefing on Russia’s nuclear threats and our Explainer on the subject.
Vessels that operate underwater. Attack submarines, capable of firing at an enemy, either use conventional fuels like diesel, or are nuclear powered. Nuclear submarines are split into two categories. SSNs are nuclear-powered, but do not have nuclear weapons. Meanwhile, SSBNs carry ballistic missiles that almost always include nuclear warheads (the “B” stands for “ballistic”). For more, read our Explainer about AUKUS, a nuclear-submarine pact.
Surveillance balloon
A largely-antiquated type of airship designed to spy from up high. Essentially a large weather balloon equipped with high-tech downward-pointing cameras. Spy balloons hover at a height of 24,000-37,000m; satellites in low-Earth orbit are around 160-2,000km up. Their lower altitude means spy balloons can take higher-quality images of the ground than satellites. In 2023 America downed a Chinese balloon sparking a diplomatic kerfuffle.

Tactical nuclear weapons
These weapons—also known as non-strategic nuclear weapons—typically have shorter ranges and smaller yields in comparison with the city-destroying “strategic” warheads mounted on intercontinental ballistic missiles. (Those typically have yields measured in the hundreds of kilotons, whereas tactical nuclear weapons can weigh in at a few kilotons, or less.) The military utility of tactical nukes is limited. For more, read our Briefing on Russia’s nuclear threats in Ukraine or our Explainer on the subject.
Thermobaric weapons
A bomb that typically comprises a core of high explosive surrounded by powdered metal such as aluminium. The explosion creates a fuel-rich cloud that continues to burn explosively as it expands. A thermobaric blast is usually longer in duration than that from a high explosive. Thermobarics are effective at demolishing structures. Their long blast pulses can also reach otherwise protected positions such as trenches or bunkers. Also known as a “vacuum bomb”. For more, read our Explainer.
Three-star general
See lieutenant general.
Two-star general
See major general.

UAS (Unmanned aerial system)
The personnel and equipment used to run an airborne drone. It encompasses not only the aircraft itself, but also the pilot on the ground and the technology that connects them.
UAV (Unmanned aerial vehicle)
See drone.
USV (Uncrewed surface vessels)
See naval drone.
UUV (Unmanned underwater vehicles)
See naval drone.

The part of an army or other military force that leads an attack.

War games
Training exercises in which military operations are simulated in order to test tactics, equipment and other aspects of a battle plan.
The front part of a missile or other projectile that contains its explosive material or chemical agent.
Weapons of mass destruction (WMD)
Nuclear, chemical, biological or radiological weapons that are intended to kill or injure large numbers of people. Though widely used by officials and politicians, the term has no precise technical or legal meaning and its use has changed over time, having once referred mainly to nuclear weapons. Nuclear and biological devices are arguably in a different category from chemical and radiological ones (“dirty bombs”) in that their mass destructive potential is greater.

The amount of energy a nuclear weapon produces when it explodes. A nuke’s yield is measured in relation to the amount of trinitrotoluene (TNT), an explosive, that would be needed to generate the same level of energy. This figure is usually given in kilotons.

“West” in Russian, and the name for regular exercises held by Russia’s armed forces. Russia used the Zapad drills in 2021 as cover to leave behind military forces that were used in the invasion of Ukraine.