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Identification, friend or foe (IFF) is an identification system designed for
command and control Command and control (abbr. C2) is a "set of organizational and technical attributes and processes ... hatemploys human, physical, and information resources to solve problems and accomplish missions" to achieve the goals of an organization o ...
. It uses a transponder that listens for an ''interrogation'' signal and then sends a ''response'' that identifies the broadcaster. IFF systems usually use
radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, Marine radar, ships, spacecraft, guided missiles, motor v ...
frequencies, but other electromagnetic frequencies, radio or infrared, may be used. It enables military and civilian
air traffic control Air traffic control (ATC) is a service provided by ground-based air traffic controllers who direct aircraft on the ground and through a given section of controlled airspace, and can provide advisory services to aircraft in non-controlled airsp ...
interrogation systems to identify aircraft, vehicles or forces as friendly and to determine their bearing and range from the interrogator. IFF is used by both military and civilian aircraft. IFF was first developed during
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
, with the arrival of radar, and several friendly fire incidents. IFF can only positively identify friendly aircraft or other forces. If an IFF interrogation receives no reply or an invalid reply, the object is not positively identified as foe; friendly forces may not properly reply to IFF for various reasons such as equipment malfunction, and parties in the area not involved in the combat, such as civilian airliners, will not be equipped with IFF. IFF is a tool within the broader military action of Combat Identification (CID), the characterization of objects detected in the field of combat sufficiently accurately to support operational decisions. The broadest characterization is that of friend, enemy, neutral, or unknown. CID not only can reduce friendly fire incidents, but also contributes to overall tactical decision-making.


History

With the successful deployment of radar systems for air defence during
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
, combatants were immediately confronted with the difficulty of distinguishing friendly aircraft from hostile ones; by that time, aircraft were flown at high speed and altitude, making visual identification impossible, and the targets showed up as featureless blips on the radar screen. This led to incidents such as the Battle of Barking Creek, over Britain,Bob Cossey, ''A Tiger's Tale: The Story of Battle of Britain Fighter Ace Wg. Cdr. John Connell Freeborn'', , chapter 4 and the
air attack on the fortress of Koepenick The air attack on the fortress of Koepenick was an incident in the air war over Germany during World War II. It took place in October 1943 and was an example of target confusion. Background On 14 October 1943 the US 8th Air Force attacked the bal ...
over Germany.Galland, Adolf : ''The First and the Last'' p 101(1954 reprinted ..) Price, Alfred : ''Battle Over the Reich'' pp95-6(1973)


British Empire


Early concepts

Already before the deployment of their Chain Home radar system (CH), the RAF had considered the problem of IFF. Robert Watson-Watt had filed patents on such systems in 1935 and 1936. By 1938, researchers at
Bawdsey Manor Bawdsey Manor stands at a prominent position at the mouth of the River Deben close to the village of Bawdsey in Suffolk, England, about northeast of London. Built in 1886, it was enlarged in 1895 as the principal residence of Sir William C ...
began experiments with "reflectors" consisting of
dipole antenna In radio and telecommunications a dipole antenna or doublet is the simplest and most widely used class of antenna. The dipole is any one of a class of antennas producing a radiation pattern approximating that of an elementary electric dipole wi ...
s tuned to resonate to the primary frequency of the CH radars. When a pulse from the CH transmitter hit the aircraft, the antennas would resonate for a short time, increasing the amount of energy returned to the CH receiver. The antenna was connected to a motorized switch that periodically shorted it out, preventing it from producing a signal. This caused the return on the CH set to periodically lengthen and shorten as the antenna was turned on and off. In practice, the system was found to be too unreliable to use; the return was highly dependent on the direction the aircraft was moving relative to the CH station, and often returned little or no additional signal. It had been suspected this system would be of little use in practice. When that turned out to be the case, the RAF turned to an entirely different system that was also being planned. This consisted of a set of tracking stations using
HF/DF High-frequency direction finding, usually known by its abbreviation HF/DF or nickname huff-duff, is a type of radio direction finder (RDF) introduced in World War II. High frequency (HF) refers to a radio band that can effectively communicate ove ...
radio direction finders. Their aircraft radios were modified to send out a 1 kHz tone for 14 seconds every minute, allowing the stations ample time to measure the aircraft's bearing. Several such stations were assigned to each "sector" of the air defence system, and sent their measurements to a plotting station at sector headquarters, who used triangulation to determine the aircraft's location. Known as "
pip-squeak Pip-squeak was a radio navigation system used by the British Royal Air Force during the early part of World War II. Pip-squeak used an aircraft's voice radio set to periodically send out a 1 kHz tone which was picked up by ground-based high- ...
", the system worked, but was labour-intensive and did not display its information directly to the radar operators. A system that worked directly with the radar was clearly desirable.


IFF Mark II

The first active IFF transponder (transmitter/responder) was the IFF Mark I which was used experimentally in 1939. This used a regenerative receiver, which fed a small amount of the amplified output back into the input, strongly amplifying even small signals as long as they were of a single frequency (like Morse code, but unlike voice transmissions). They were tuned to the signal from the CH radar (20–30 MHz), amplifying it so strongly that it was broadcast back out the aircraft's antenna. Since the signal was received at the same time as the original reflection of the CH signal, the result was a lengthened "blip" on the CH display which was easily identifiable. In testing, it was found that the unit would often overpower the radar or produce too little signal to be seen, and at the same time, new radars were being introduced using new frequencies. Instead of putting Mark I into production, a new IFF Mark II was introduced in early 1940. Mark II had a series of separate tuners inside tuned to different radar bands that it stepped through using a motorized switch, while an
automatic gain control Automatic gain control (AGC) is a closed-loop feedback regulating circuit in an amplifier or chain of amplifiers, the purpose of which is to maintain a suitable signal amplitude at its output, despite variation of the signal amplitude at the inpu ...
solved the problem of it sending out too much signal. Mark II was technically complete as the war began, but a lack of sets meant it was not available in quantity and only a small number of RAF aircraft carried it by the time of the
Battle of Britain The Battle of Britain, also known as the Air Battle for England (german: die Luftschlacht um England), was a military campaign of the Second World War, in which the Royal Air Force (RAF) and the Fleet Air Arm (FAA) of the Royal Navy defende ...
. Pip-squeak was kept in operation during this period, but as the Battle ended, IFF Mark II was quickly put into full operation. Pip-squeak was still used for areas over land where CH did not cover, as well as an emergency guidance system.


IFF Mark III

Even by 1940 the complex system of Mark II was reaching its limits while new radars were being constantly introduced. By 1941, a number of sub-models were introduced that covered different combinations of radars, common naval ones for instance, or those used by the RAF. But the introduction of radars based on the
microwave Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ra ...
-frequency cavity magnetron rendered this obsolete; there was simply no way to make a responder operating in this band using contemporary electronics. In 1940, English engineer Freddie Williams had suggested using a single separate frequency for all IFF signals, but at the time there seemed no pressing need to change the existing system. With the introduction of the magnetron, work on this concept began at the Telecommunications Research Establishment as the IFF Mark III. This was to become the standard for the Western Allies for most of the war. Mark III transponders were designed to respond to specific 'interrogators', rather than replying directly to received radar signals. These interrogators worked on a limited selection of frequencies, no matter what radar they were paired with. The system also allowed limited communication to be made, including the ability to transmit a coded '
Mayday Mayday is an emergency procedure word used internationally as a distress signal in voice-procedure radio communications. It is used to signal a life-threatening emergency primarily by aviators and mariners, but in some countries local organiz ...
' response. The IFF sets were designed and built by
Ferranti Ferranti or Ferranti International plc was a UK electrical engineering and equipment firm that operated for over a century from 1885 until it went bankrupt in 1993. The company was once a constituent of the FTSE 100 Index. The firm was known ...
in
Manchester Manchester () is a city in Greater Manchester, England. It had a population of 552,000 in 2021. It is bordered by the Cheshire Plain to the south, the Pennines to the north and east, and the neighbouring city of Salford to the west. The ...
to Williams' specifications. Equivalent sets were manufactured in the US, initially as copies of British sets, so that allied aircraft would be identified upon interrogation by each other's radar. IFF sets were obviously highly classified. Thus, many of them were wired with explosives in the event the aircrew bailed out or crash landed. Jerry Proc reports:


Germany

FuG 25a ''Erstling'' (English: Firstborn, Debut) was developed in Germany in 1940. It was tuned to the low-
VHF Very high frequency (VHF) is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) from 30 to 300 megahertz (MHz), with corresponding wavelengths of ten meters to one meter. Frequencies immediately below VHF ...
band at 125 MHz used by the Freya radar, and an adaptor was used with the low-
UHF Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter (on ...
-banded 550–580 MHz used by Würzburg. Before a flight, the transceiver was set up with a selected day code of ten bits which was dialed into the unit. To start the identification procedure, the ground operator switched the pulse frequency of his radar from 3,750 Hz to 5,000 Hz. The airborne receiver decoded that and started to transmit the day code. The radar operator would then see the blip lengthen and shorten in the given code. The IFF transmitter worked on 168 MHz with a power of 400 watts (PEP). The system included a way for ground controllers to determine whether an aircraft had the right code or not but it did not include a way for the transponder to reject signals from other sources. British military scientists found a way of exploiting this by building their own IFF transmitter called
Perfectos Perfectos was a radio device used by Royal Air Force's night fighters during the Second World War to detect German aircraft. It worked by triggering '' Luftwaffe's'' FuG 25a Erstling identification friend or foe (IFF) system and then using the re ...
, which were designed to trigger a response from any FuG 25a system in the vicinity. When an FuG 25a responded on its 168 MHz frequency, the signal was received by the antenna system from an AI Mk. IV radar, which originally operated at 212 MHz. By comparing the strength of the signal on different antennas the direction to the target could be determined. Mounted on Mosquitos, the "Perfectos" severely limited German use of the FuG 25a.


Further wartime developments


IFF Mark IV and V

The
United States Naval Research Laboratory The United States Naval Research Laboratory (NRL) is the corporate research laboratory for the United States Navy and the United States Marine Corps. It was founded in 1923 and conducts basic scientific research, applied research, technological ...
had been working on their own IFF system since before the war. It used a single interrogation frequency, like the Mark III, but differed in that it used a separate responder frequency. Responding on a different frequency has several practical advantages, most notably that the response from one IFF cannot trigger another IFF on another aircraft. But it requires a complete transmitter for the responder side of the circuitry, in contrast to the greatly simplified regenerative system used in the British designs. This technique is now known as a cross-band transponder. When the Mark II was revealed in 1941 during the Tizard Mission, it was decided to use it and take the time to further improve their experimental system. The result was what became IFF Mark IV. The main difference between this and earlier models is that it worked on higher frequencies, around 600 MHz, which allowed much smaller antennas. However, this also turned out to be close to the frequencies used by the German Würzburg radar and there were concerns that it would be triggered by that radar and the transponder responses would be picked on its radar display. This would immediately reveal the IFF's operational frequencies. This led to a US–British effort to make a further improved model, the Mark V, also known as the United Nations Beacon or UNB. This moved to still higher frequencies around 1 GHz but operational testing was not complete when the war ended. By the time testing was finished in 1948, the much improved Mark X was beginning its testing and Mark V was abandoned.


Postwar systems


IFF Mark X

Mark X started as a purely experimental device operating at frequencies above 1 GHz, the name refers to "experimental", not "number 10". As development continued it was decided to introduce an encoding system known as the "Selective Identification Feature", or SIF. SIF allowed the return signal to contain up to 12 pulses, representing four
octal The octal numeral system, or oct for short, is the radix, base-8 number system, and uses the Numerical digit, digits 0 to 7. This is to say that 10octal represents eight and 100octal represents sixty-four. However, English, like most languages, ...
digits of 3 bits each. Depending on the timing of the interrogation signal, SIF would respond in several ways. Mode 1 indicated the type of aircraft or its mission (cargo or bomber, for instance) while Mode 2 returned a tail code. Mark X began to be introduced in the early 1950s. This was during a period of great expansion of the civilian air transport system, and it was decided to use slightly modified Mark X sets for these aircraft as well. These sets included a new military Mode 3 which was essentially identical to Mode 2, returning a four-digit code, but used a different interrogation pulse, allowing the aircraft to identify if the query was from a military or civilian radar. For civilian aircraft, this same system was known as Mode A, and because they were identical, they are generally known as Mode 3/A. Several new modes were also introduced during this process. Civilian modes B and D were defined, but never used. Mode C responded with a 12-bit number encoded using Gillham code, which represented the altitude as (that number) x 100 feet - 1200. Radar systems can easily locate an aircraft in two dimensions, but measuring altitude is a more complex problem and, especially in the 1950s, added significantly to the cost of the radar system. By placing this function on the IFF, the same information could be returned for little additional cost, essentially that of adding a digitizer to the aircraft's altimeter. Modern interrogators generally send out a series of challenges on Mode 3/A and then Mode C, allowing the system to combine the identity of the aircraft with its altitude and location from the radar.


IFF Mark XII

The current IFF system is the Mark XII. This works on the same frequencies as Mark X, and supports all of its military and civilian modes. It had long been considered a problem that the IFF responses could be triggered by any properly formed interrogation, and those signals were simply two short pulses of a single frequency. This allowed enemy transmitters to trigger the response, and using triangulation, an enemy could determine the location of the transponder. The British had already used this technique against the Germans during WWII, and it was used by the USAF against
VPAF The Vietnam People's Air Force (VPAF, ), formally refers itself as the Air Defence - Air Force (ADAF, ) or the Vietnamese Air Force (VNAF, ), is the aerial warfare service branch of Vietnam. It is the successor of the former North Vietnamese ...
aircraft during the
Vietnam War The Vietnam War (also known by #Names, other names) was a conflict in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. It was the second of the Indochina Wars and was officially fought between North Vie ...
. Mark XII differs from Mark X through the addition of the new military Mode 4. This works in a fashion similar to Mode 3/A, with the interrogator sending out a signal that the IFF responds to. There are two key differences, however. One is that the Interrogation pulse is followed by a 12-bit code similar to the ones sent back by the Mark 3 transponders. The encoded number changes day-to-day. When the number is received and decoded in the aircraft transponder, a further cryptographic encoding is applied. If the result of that operation matches the value dialled into the IFF in the aircraft, the transponder replies with a Mode 3 response as before. If the values do not match, it does not respond. This solves the problem of the aircraft transponder replying to false interrogations, but does not completely solve the problem of locating the aircraft through triangulation. To solve this problem, a delay is added to the response signal that varies based on the code sent from the interrogator. When received by an enemy that does not see the interrogation pulse, which is generally the case as they are often below the
radar horizon The radar horizon is a critical area of performance for aircraft detection systems that is defined by the distance at which the radar beam rises enough above the Earth's surface to make detection of a target at low level impossible. It is asso ...
, this causes a random displacement of the return signal with every pulse. Locating the aircraft within the set of returns is a difficult process.


Mode S

During the 1980s, a new civilian mode, Mode S, was added that allowed greatly increased amounts of data to be encoded in the returned signal. This was used to encode the location of the aircraft from the navigation system. This is a basic part of the traffic collision avoidance system (TCAS), which allows commercial aircraft to know the location of other aircraft in the area and avoid them without the need for ground operators. The basic concepts from Mode S were then militarized as Mode 5, which is simply a cryptographically encoded version of the Mode S data. The IFF of
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
and Soviet military systems (1946 to 1991) used coded
radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, Marine radar, ships, spacecraft, guided missiles, motor v ...
signals (called Cross-Band Interrogation, or CBI) to automatically trigger the aircraft's transponder in an aircraft illuminated by the radar. Radar-based aircraft identification is also called secondary surveillance radar in both military and civil usage, with primary radar bouncing an RF pulse off of the aircraft to determine position. George Charrier, working for RCA, filed for a
patent A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an enabling disclosure of the invention."A ...
for such an IFF device in 1941. It required the operator to perform several adjustments to the radar receiver to suppress the image of the natural echo on the radar receiver, so that visual examination of the IFF signal would be possible. By 1943, Donald Barchok filed a patent for a radar system using the abbreviation IFF in his text with only parenthetic explanation, indicating that this acronym had become an accepted term. In 1945, Emile Labin and Edwin Turner filed patents for radar IFF systems where the outgoing radar signal and the transponder's reply signal could each be independently programmed with a binary codes by setting arrays of toggle switches; this allowed the IFF code to be varied from day to day or even hour to hour.


Early 21st century systems


NATO

The United States and other NATO countries started using a system called Mark XII in the late twentieth century; Britain had not until then implemented an IFF system compatible with that standard, but then developed a program for a compatible system known as successor IFF (SIFF).


Modes

* Mode 1 – military only; provides 2-digit octal (6 bit) "mission code" that identifies the aircraft type or mission.
NATO The North Atlantic Treaty Organization (NATO, ; french: Organisation du traité de l'Atlantique nord, ), also called the North Atlantic Alliance, is an intergovernmental military alliance between 30 member states – 28 European and two N ...
STANAG 4193
* Mode 2 – military only; provides 4-digit octal (12 bit) unit code or tail number. * Mode 3/A – military/civilian; provides a 4-digit octal (12 bit) identification code for the aircraft, assigned by the air traffic controller. Commonly referred to as a squawk code. * Mode 4 – military only; provides a 3-pulse reply, delay is based on the encrypted challenge. * Mode 5 – military only; provides a cryptographically secured version of Mode S and ADS-B GPS position. Modes 4 and 5 are designated for use by
NATO The North Atlantic Treaty Organization (NATO, ; french: Organisation du traité de l'Atlantique nord, ), also called the North Atlantic Alliance, is an intergovernmental military alliance between 30 member states – 28 European and two N ...
forces.


Submarines

In
World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was List of wars and anthropogenic disasters by death toll, one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, ...
, 8 submarines were sunk by friendly fire and in
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
nearly 20 were sunk this way. Still,
Identification of friend or foe Identification, friend or foe (IFF) is an identification system designed for command and control. It uses a transponder that listens for an ''interrogation'' signal and then sends a ''response'' that identifies the broadcaster. IFF systems usual ...
(IFF) has not been regarded a high concern before the 1990s by the US military as not many other countries possess submarines. IFF methods that are analogous to aircraft IFF have been deemed unfeasible for submarines because they would make submarines easier to detect. Thus, having friendly submarines broadcast a signal, or somehow increase the submarine's signature (based on acoustics, magnetic fluctuations etc.), are not considered viable. Instead, submarine IFF is done based on carefully defining areas of operation. Each friendly submarine is assigned a patrol area, where the presence of any other submarine is deemed hostile and open to attack. Further, within these assigned areas, surface ships and aircraft refrain from any
anti-submarine warfare Anti-submarine warfare (ASW, or in older form A/S) is a branch of underwater warfare that uses surface warships, aircraft, submarines, or other platforms, to find, track, and deter, damage, or destroy enemy submarines. Such operations are typ ...
(ASW); only the resident submarine may target other submarines in its own area. Ships and aircraft may still engage in ASW in areas that have not been assigned to any friendly submarines. Navies also use database of acoustic signatures to attempt to identify the submarine, but acoustic data can be ambiguous and several countries deploy similar classes of submarines.


Highly visible painted IFF markings

Painted colours or bands have been used as an easy and low-tech combat identification system. The most notable example comes from the
Normandy landings The Normandy landings were the landing operations and associated airborne operations on Tuesday, 6 June 1944 of the Allied invasion of Normandy in Operation Overlord during World War II. Codenamed Operation Neptune and often referred to as ...
in
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
, where invasion stripes were used. These were alternating black and white bands painted on the
fuselage The fuselage (; from the French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds crew, passengers, or cargo. In single-engine aircraft, it will usually contain an engine as well, although in some amphibious aircraft t ...
and wings of Allied aircraft to reduce the chance that they would be attacked by friendly forces during and after the landings. Three white and two black bands were wrapped around the rear of a fuselage just in front of the
empennage The empennage ( or ), also known as the tail or tail assembly, is a structure at the rear of an aircraft that provides stability during flight, in a way similar to the feathers on an arrow.Crane, Dale: ''Dictionary of Aeronautical Terms, third e ...
(tail) and from front to back around the upper and lower wing surfaces.


World War II

Invasion stripes were five alternating black and white stripes. On single-engine aircraft each stripe was to be wide, placed inboard of the roundels on the wings and forward of the leading edge of the tailplane on the fuselage.
National markings Military aircraft insignia are insignia applied to military aircraft to identify the nation or branch of military service to which the aircraft belong. Many insignia are in the form of a circular roundel or modified roundel; other shapes such as ...
and serial number were not to be obliterated. On twin-engine aircraft the stripes were wide, placed outboard of the engine
nacelles A nacelle ( ) is a "streamlined body, sized according to what it contains", such as an engine, fuel, or equipment on an aircraft. When attached by a pylon entirely outside the airframe, it is sometimes called a pod, in which case it is attached ...
on the wings, and forward of the leading edge of the tailplane around the fuselage. However, American aircraft using the invasion stripes very commonly had some part of the added "bar" section of their post-1942 roundels overlapping the invasion strips on the wings.


Korean War

Invasion stripes were re-introduced on British and
Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...
n
Fleet Air Arm The Fleet Air Arm (FAA) is one of the five fighting arms of the Royal Navy and is responsible for the delivery of naval air power both from land and at sea. The Fleet Air Arm operates the F-35 Lightning II for maritime strike, the AW159 Wi ...
aircraft operating during the
Korean War {{Infobox military conflict , conflict = Korean War , partof = the Cold War and the Korean conflict , image = Korean War Montage 2.png , image_size = 300px , caption = Clockwise from top:{ ...
in 1950. Similar stripes were also used early in the war on F-86 Sabres of the
4th Fighter Interceptor Wing The 4th Fighter Wing is a United States Air Force unit assigned to the Air Combat Command's Ninth Air Force. It is stationed at Seymour Johnson Air Force Base, North Carolina, where it is also the host unit. The wing is one of two Air Force uni ...
as a deviation from the standard yellow stripes.


Suez operation

The stripes were used again by the
Royal Air Force The Royal Air Force (RAF) is the United Kingdom's air and space force. It was formed towards the end of the First World War on 1 April 1918, becoming the first independent air force in the world, by regrouping the Royal Flying Corps (RFC) an ...
, the Royal Navy's
Fleet Air Arm The Fleet Air Arm (FAA) is one of the five fighting arms of the Royal Navy and is responsible for the delivery of naval air power both from land and at sea. The Fleet Air Arm operates the F-35 Lightning II for maritime strike, the AW159 Wi ...
, the French Naval Aviation and the French Air Force during the Suez operation of 1956, mostly to distinguish UK and French aircraft from Egypt's British-made planes. Single-engined aircraft had yellow/black/yellow/black/yellow stripes one foot wide; multi-engined aircraft had the same pattern with stripes. Israel, who was a co-belligerent with Britain and France, did not paint Suez Stripes on their aircraft.


Invasion of Czechoslovakia

During the Soviet-led invasion of Czechoslovakia in 1968, the Soviet Union used a series of white stripes on the armoured vehicles of its invasion forces because they used predominantly the same types of combat vehicles as the armed forces of
Czechoslovakia , rue, Чеськословеньско, , yi, טשעכאסלאוואקיי, , common_name = Czechoslovakia , life_span = 1918–19391945–1992 , p1 = Austria-Hungary , image_p1 ...
(both were
Warsaw Pact The Warsaw Pact (WP) or Treaty of Warsaw, formally the Treaty of Friendship, Cooperation and Mutual Assistance, was a collective defense treaty signed in Warsaw, Poland, between the Soviet Union and seven other Eastern Bloc socialist republi ...
allies). The markings consisted of one long white strip in the middle of the vehicle from the front and across the roof all the way to the back with two additional strips in the middle of both sides. This is similar to the markings applied on most Soviet tanks and armoured fighting vehicles fighting in Berlin in 1945 during the
Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposi ...
to prevent friendly fire from Western Allied (British or American) aircraft that flew over the city to conduct bombing raids until its fall. In addition to that, certain Soviet Air Force aircraft, such as the MiG-21 fighters, were given two red stripes on their fuselages and vertical stabilisers, also because these types of aircraft were used by the Czechoslovak Air Force.


Russian invasion of Ukraine

Several white painted letters, most famously an insignia resembling the Latin letter Z, have been used on tanks and armoured vehicles by the Russian Armed Forces during the 2022 Invasion of Ukraine. In April 2021, analysts first noted that vehicles were being painted with markings similar to those used in the invasion of
Czechoslovakia , rue, Чеськословеньско, , yi, טשעכאסלאוואקיי, , common_name = Czechoslovakia , life_span = 1918–19391945–1992 , p1 = Austria-Hungary , image_p1 ...
. Military experts and advisors have stated that this is likely to prevent friendly fire incidents, as both the Russian and Ukrainian forces use the same type of combat vehicles. The Russian Ministry of Defence confirmed the symbol's usage on Instagram, stating it is an abbreviation of the phrase "for the victory" (russian: за победу, za pobedu). According to the
Armed Forces of Ukraine , imports = , exports = , history = , ranks = Military ranks of Ukraine , country=Ukraine The Armed Forces of Ukraine ( uk, Збро́йні си́ли Украї́ни), most commonly know ...
, the different letters indicate different Russian military detachments, with the Z indicating forces from the Eastern Military District.


See also

* Automatic target recognition *
Challenge–response authentication In computer security, challenge–response authentication is a family of protocols in which one party presents a question ("challenge") and another party must provide a valid answer ("response") to be authenticated. The simplest example of a ch ...
*
Cryptography Cryptography, or cryptology (from grc, , translit=kryptós "hidden, secret"; and ''graphein'', "to write", or '' -logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of adv ...
* List of World War II electronic warfare equipment *
Radio-frequency identification Radio-frequency identification (RFID) uses electromagnetic fields to automatically Automatic identification system, identify and Tracking system, track tags attached to objects. An RFID system consists of a tiny radio transponder, a radio receiver ...
* Secondary surveillance radar *
Squawk code A transponder (short for ''trans''mitter-res''ponder'' and sometimes abbreviated to XPDR, XPNDR, TPDR or TP) is an electronic device that produces a response when it receives a radio-frequency interrogation. Aircraft have transponders to assist ...
* Transponder *
Non-Cooperative Target Recognition Radar MASINT is a subdiscipline of measurement and signature intelligence (MASINT) and refers to intelligence gathering activities that bring together disparate elements that do not fit within the definitions of signals intelligence (SIGINT), im ...
*
Combat Identification Panel The Combat Identification Panel (CIP), also known as a Coalition Identification Panel, is an Identification friend or foe device mounted on military ground vehicles used by United States Armed Forces' United States Army with United States Marine ...
*
Nelson Chequer The Nelson Chequer was a colour scheme adopted by vessels of the Royal Navy, modelled on that used by Admiral Horatio Nelson in battle. It consisted of bands of black and yellow paint along the sides of the hull, broken up by black gunports. I ...
, early 19th-century identification pattern * Invasion stripes


References

* *


External links

*
Overview of SSR and IFF Systems
{{DEFAULTSORT:Identification Friend Or Foe Military communications Radio-frequency identification Avionics Authentication methods