Electromagnetic warfare
The electromagnetic environment: Military operations are executed in an information environment increasingly complicated by the electromagnetic spectrum. The electromagnetic spectrum portion of the information environment is referred to as the electromagnetic environment (EME). The recognized need for military forces to have unimpeded access to and use of the electromagnetic environment creates vulnerabilities and opportunities for electronic warfare in support of military operations.
Within the information operations construct, EW is an element of information warfare; more specifically, it is an element of offensive and defensive counterinformation.
NATO has a different and arguably more encompassing and comprehensive approach to EW. A military committee conceptual document from 2007, MCM_0142 Nov 2007 Military Committee Transformation Concept for Future NATO Electronic Warfare, recognised the EME as an operational maneuver space and warfighting environment/domain. In NATO, EW is considered to be warfare in the EME. NATO has adopted simplified language which parallels those used in other warfighting environments like maritime, land, and air/space. For example, an electronic attack (EA) is offensive use of EM energy, electronic defense (ED), and electronic surveillance (ES). The use of the traditional NATO EW terms, electronic countermeasures (ECM), electronic protective measures (EPM), and electronic support measures (ESM) has been retained as they contribute to and support electronic attack (EA), electronic defense (ED) and electronic surveillance (ES). Besides EW, other EM operations include intelligence, surveillance, target acquisition and reconnaissance (ISTAR), and signals intelligence (SIGINT). Subsequently, NATO has issued EW policy and doctrine and is addressing the other NATO defense lines of development.
Primary EW activities have been developed over time to exploit the opportunities and vulnerabilities that are inherent in the physics of EM energy. Activities used in EW include electro-optical, infrared and radio frequency countermeasures; EM compatibility and deception; radio jamming, radar jamming and deception and electronic counter-countermeasures (or anti-jamming); electronic masking, probing, reconnaissance, and intelligence; electronic security; EW reprogramming; emission control; spectrum management; and wartime reserve modes.

Subdivisions: Electronic warfare consists of three major subdivisions: electronic attack (EA), electronic protection (EP), and electronic warfare support (ES).

Electronic attack: Electronic attack (EA), also known as electronic countermeasures (ECM), involves the offensive use of electromagnetic energy weapons, directed energy weapons, or anti-radiation weapons to attack personnel, facilities, or equipment with the intent of degrading, neutralizing, or destroying enemy combat capability including human life. In the case of electromagnetic energy, this action is most commonly referred to as "jamming" and can be performed on communications systems or radar systems. In the case of anti-radiation weapons, this often includes missiles or bombs that can home in on a specific signal (radio or radar) and follow that path directly to impact, thus destroying the system broadcasting.
In November 2021, Israel Aerospace Industries announced a new electronic warfare system named Scorpius that can disrupt radar and communications from ships, UAVs, and missiles simultaneously and at varying distances.
On 8 September 2024, Russian drones entered both Romanian and Latvian airspace. Romanian scrambled two F-16s to monitor the drone's progress, it landed "in an uninhabited area" near Periprava, according to the Romanian Ministry of Defence. The drone that entered Latvian airspace from Belarus crashed near Rezekne. This comes as the ISW noted increased success in Ukrainian Electronic Warfare against Russian drones that resulted in "several Russian Shahed drones (that) recently failed to reach their intended targets for unknown reasons." Two Kh-58s also reportedly failed to reach their targets.

Electronic protection: Electronic protection (EP), also known as an electronic protective measure (EPM) or electronic counter-countermeasure (ECCM) are a measure used to protect against an electronic enemy attack (EA) or to protect against friendly forces who unintentionally deploy the equivalent of an electronic attack on friendly forces. (sometimes called EW fratricide). The effectiveness of electronic protection (EP) level is the ability to counter an electronic attack (EA).
Flares are often used to distract infrared homing missiles into missing their target. The use of flare rejection logic in the guidance (seeker head) of an infrared homing missile to counter an adversary's use of flares is an example of EP. While defensive EA actions (jamming) and EP (defeating jamming) both protect personnel, facilities, capabilities, and equipment, EP protects from the effects of EA (friendly and/or adversary). Other examples of EP include spread spectrum technologies, the use of restricted frequency lists, emissions control (EMCON), and low observability (stealth) technology.
Electronic warfare self-protection (EWSP) is a suite of countermeasure systems fitted primarily to aircraft for the purpose of protecting the host from weapons fire and can include, among others: directional infrared countermeasures (DIRCM, flare systems and other forms of infrared countermeasures for protection against infrared missiles; chaff (protection against radar-guided missiles); and DRFM decoy systems (protection against radar-targeted anti-aircraft weapons).
An electronic warfare tactics range (EWTR) is a practice range that provides training for personnel operating in electronic warfare. There are two examples of such ranges in Europe: one at RAF Spadeadam in the northwest county of Cumbria, England, and the Multinational Aircrew Electronic Warfare Tactics Facility Polygone range on the border between Germany and France. EWTRs are equipped with ground-based equipment to simulate electronic warfare threats that aircrew might encounter on missions. Other EW training and tactics ranges are available for ground and naval forces as well.
Antifragile EW is a step beyond standard EP, occurring when a communications link being jammed actually increases in capability as a result of a jamming attack, although this is only possible under certain circumstances such as reactive forms of jamming.

Electronic warfare support: Electronic warfare support (ES) is a subdivision of EW involving actions taken by an operational commander or operator to detect, intercept, identify, locate, and/or localize sources of intended and unintended radiated electromagnetic (EM) energy.  These Electronic Support Measures (ESM) aim to enable immediate threat recognition focuses on serving military service needs even in the most tactical, rugged, and extreme environments.  This is often referred to as simply reconnaissance, although today, more common terms are intelligence, surveillance and reconnaissance (ISR) or intelligence, surveillance, target acquisition, and reconnaissance (ISTAR). The purpose is to provide immediate recognition, prioritization, and targeting of threats to battlefield commanders.
Signals intelligence (SIGINT), a discipline overlapping with ES, is the related process of analyzing and identifying intercepted transmissions from sources such as radio communication, mobile phones, radar, or microwave communication. SIGINT is broken into two categories: electronic intelligence (ELINT) and communications intelligence (COMINT). Analysis parameters measured in signals of these categories can include frequency, bandwidth, modulation, and polarization.
The distinction between SIGINT and ES is determined by the controller of the collection assets, the information provided, and the intended purpose of the information. Electronic warfare support is conducted by assets under the operational control of a commander to provide tactical information, specifically threat prioritization, recognition, location, targeting, and avoidance. However, the same assets and resources that are tasked with ES can simultaneously collect information that meets the collection requirements for more strategic intelligence.

History: The earliest documented use of EW was during the Second Boer War of 1899–1902. The British Army, when trying to relieve Ladysmith, under siege by the Boers, used a searchlight to "bounce" Morse code signals off the clouds. The Boers immediately spotted this and used one of their own searchlights in an attempt to jam the British signals. This was graphically described by Winston Churchill in his book London to Ladysmith via Pretoria. 
During the Russo-Japanese War of 1904–1905 the Japanese auxiliary cruiser Shinano Maru had located the Russian Baltic Fleet in Tsushima Strait, and was communicating the fleet's location by radio signals to the Imperial Japanese Fleet HQ. The captain of the Russian warship Ural requested permission to disrupt the Japanese communications link by attempting to transmit a stronger radio signal over the Shinano Maru's signal, hoping to distort the Japanese signal at the receiving end. Russian Admiral Zinovy Rozhestvensky refused the advice and denied the Ural permission to electronically jam the enemy, which in those circumstances might have proved invaluable. The intelligence the Japanese gained ultimately led to the decisive Battle of Tsushima, where the Russian Navy lost all its battleships and most of its cruisers and destroyers. These losses effectively ended the Russo-Japanese War in Japan's favor.
During World War II, the Allies and Axis Powers both extensively used EW, or what Winston Churchill referred to as the "Battle of the Beams": as navigational radars were used to guide bombers to their targets and back to their base, the first application of EW in WWII was to interfere with the navigational radars. Chaff was also introduced during WWII to confuse and defeat tracking radar systems.
As battlefield communication and radar technology improved, so did electronic warfare, which played a major role in several military operations during the Vietnam War. Aircraft on bombing runs and air-to-air missions often relied on EW to survive the battle, although many were defeated by Vietnamese ECCM.