Espionage is the practice of obtaining secrets (spying) from rivals or enemies for military, political, or economic advantage. It is usually thought of as part of an institutional effort (i.e., governmental or corporate intelligence). The definition has been restricted to a state spying on potential or actual enemies, primarily for military purposes, but this has been extended to spying involving corporations, known specifically as industrial espionage. Many nations routinely spy on both their enemies, and allies, although they maintain a policy of not making comment on this. Black's Law Dictionary (1990) defines espionage as: "...gathering, transmitting, or losing...information related to the national defense."

A spy is an agent employed to obtain such secrets. The term intelligence officer is also used to describe a member of the armed forces, police officer or civilian intelligence agency who specialises in the gathering, fusion and analysis of information and intelligence in order to provide advice to their government or another organisation.

Incidents of espionage are well documented throughout history. The writings of Sun-Tzu contains information on deception and subversion. The ancient Egyptians had a thoroughly developed system for the acquisition of intelligence, and the Hebrews used spies as well. More recently, they played a significant part in Elizabethan England (see Francis Walsingham). Feudal Japan often used ninja to gather intelligence. Many modern espionage methods were already then well established.[1]

Espionage, when performed by a citizen of the target state, is generally considered to be a form of treason. In many countries espionage is a crime punishable by death or life imprisonment. For example, espionage is still a capital crime in the USA; however, the death penalty is rarely used in espionage cases in the U.S. See Espionage Act.

In a person who owed allegiance to the British Crown who spied for a foreign country would face a maximum life sentence for treason if it could be proved they were aiding Britain's enemies. In fact a foreign spy may also be prosecuted for treason because temporary allegiance to the Crown is owed by everyone voluntarily in Britain except lawful enemy combatants.

Spying for proscribed terrorist organisations violates the Terrorism Act 2000. During the Second World War German spies in Britain were executed for treachery, a special offense covering any aid given to the enemy, including by foreign nationals.

The Cold War involved intense espionage activity between the United States of America and its allies and the Soviet Union and the People's Republic of China and their allies, particularly related to nuclear weapons secrets. Recently, espionage agencies have targeted the illegal drug trade and those considered to be terrorists.


Noteworthy incidents in the history of espionage
Betrayal of Joan of Arc by English-serving spy Bishop Pierre Cauchon of Beauvais 
Daniel Defoe spies for England in Edinburgh, assisting in the bribery scandal which led to the Treaty of Union 1707. 
Benedict Arnold's West Point betrayal conspiracy 
Patriot Kelsie DeNooy leaks British invasion plan to General Washington. 
1870s -- Infiltration of US labor unions by Pinkerton National Detective Agency 
1940s -- Double Cross System British capture of German spy network in Britain in WW II 
1940s -- Transfer of US nuclear weapons secrets in the Rosenberg Case 
1940s - 1950s -- Cambridge Five Soviet spy ring in UK during and after WW II 
1961 -- Failure of the Bay of Pigs Invasion 
1968 - 1985 -- Walker spy ring sold U.S. KL-7 codes to Soviets 
1970s - 1990s -- Alleged Chinese theft of American nuclear weapons designs (See Cox Report) 
2005 -- Leandro Aragoncillo indicted as part of what the FBI refers to as the first case in history of espionage from within the White House. 


Espionage organizations
Main article List of intelligence agencies. 
Australia: DSD, ASIO, ASIS, ONA, DIO 
Canada: CSIS, CSE 
Germany: BND 
India: RAW, IB, JIC, DIA 
Israel: Mossad 
Italy: SISMI, SISDE 
Pakistan: ISI 
New Zealand: NZSIS 
South Africa: NIA, SASS, SANDF-ID 
Soviet Union: KGB (several previous/subsequent names); Soviet Military Intelligence GRU 
UK: MI5, MI6, GCHQ, Special Branch 
USA: CIA, DIA, NSA, NRO 
See also Intelligence agency and Special Operations Executive 

Espionage technology and techniques
Main article list of intelligence gathering disciplines. 
ECHELON 
Agent Handling 
Black Bag Operations 
Concealment device 
Cryptography 
Cut-out 
Dead drop 
Eavesdropping 
False flag operations 
Honey trap 
Interrogation 
Nonofficial cover - NOC 
One Time Pad 
One Way Voice Link 
Steganography 
Surveillance 
TEMPEST — Protection devices for communication equipment. 

Spy fiction
Main article: Spy fiction 
Since not much is publicly known about real-life secret agents, the popular conception of the secret agent has been formed largely by 20th and 21st century literature and cinema. Similar to the character of the private eye, the secret agent is usually a loner, sometimes amoral, an existential hero operating outside the everyday constraints of society. James Bond, the protagonist of Ian Fleming's novels who went on to spawn an extremely successful film franchise, is probably the most famous fictional secret agent of all.

Spy Fiction has also become prevalent in video gaming, where the "wetworks" aspect of espionage is highlighted. Game situations typically involve agents sent into enemy territory for purposes of subversion. These depictions are more action-oriented than would be typical in most cases of espionage, and they tend to focus on infiltration rather than information-gathering.