Intelligence
    
    Intelligence is in government operations, evaluated information concerning such things as the strength, activities, and probable courses of action of other nations who are usually, but not necessarily, opponents. In a world of sovereign nations, information is a prime element of national power, and intelligence is the vital and often pivotal foundation for national decisions.
    National intelligence organizations
    In a world in revolutionary ferment, the authentic intelligence officer occupies the centre of great debates over national security policy. At issue in most of the debates are questions of power, probability, and time. A prime task of the modem professional intelligence officer, military or civilian, is to try to answer questions for the policymaker about power and about behaviour probabilities, within a time scale. For a chief of state trying to decide a question about nuclear armaments, for example, an ideal intelligence system would provide precise knowledge of a potential enemy's power, the probability of that enemy's behaviour or reaction in given contingencies, and a time schedule for the most likely sequence of events.
    These are basic problems for all intelligence services. Information as to how these services address their problems is highly uneven. More is generally known about the U.S. system than any other, a good deal about that of the old Soviet Union, and comparatively less about other systems. Intelligence systems follow three general models: the U.S., which was followed by former West Germany, Japan, South Korea, and other nations that came under U.S. influence after World War II; the old Soviet, which was imitated in large measure by most communist-governed nations; and the British, on which were patterned the systems of most nations with true parliamentary governments.
    The United Kingdom
    British intelligence was organized along modem lines as early as the days of Queen Elizabeth I, and the long British experience has influenced the structure of most other systems. Unlike those of the United States and the old Soviet Union, British intelligence agencies have preserved through most of their history a high degree of secrecy concerning their organization and operations. Even so, Britain has suffered from large number of native spies within the intelligence establishment.
    The two principal British intelligence agencies are the Secret Intelligence Service (SIS; also known by its wartime designation, MI-6) and the Security Service (commonly called MI-5). The labels derive from the fact that the Secret Intelligence Service was once "section six" of military intelligence and the Security Service, "section five."
    
    MI-6
    MI-6 is the formally Secret Intelligence Service, British government agency responsible for the collection, analysis, and appropriate dissemination of foreign intelligence. MI-6 is responsible for the conduct of espionage activities outside British territory.
    The Intelligence Services Act 1994 defines the role of MI6 as "a) to obtain and provide information relating to the actions or intentions of persons outside the British Islands; and
    b) to perform other tasks relating to the actions or intentions of such persons...[in relation to]
    the interests of national security, with particular reference to defence and foreign policies...the interests of the economic well-being of the UK...or in support of the prevention or detection of serious crime."
    MI-6 has existed, in various forms since the establishment of a secret service in 1569 by Sir Francis Walsingham, who became secretary of state to Queen Elizabeth I. It was constituted in its present form by Commander (later Sir) Mansfield Cumming in 1912 as World War I approached. In the 1930s and 1940s it was considered the most effective intelligence service in the world. During the rise of Nazi Germany, MI-6 conducted espionage operations in Europe, Latin America, and much of Asia. (The "MI-6" label developed during this period because it was then "section six" of "military intelligence.")
    When the United States entered World War II, the British agency helped train personnel of the U.S. Office of Strategic Services and has since cooperated with the successor Central Intelligence Agency (CIA). The revelation in the mid-1950s that MI-6 had been penetrated by British double agents who had served the Soviet Union since the 1930s stirred wide public consternation. Details of MI-6 operations and relationships seldom appear in the British press. The agency has the power to censor such stories through the use of "D" notices under the Official Secrets Act. MI-6 reports to the Foreign Office.
    
    Another branch of British intelligence system is MI-5.
    
    MI-5
    MI-5 is the formally Security Service, intelligence agency charged with internal security and domestic counterintelligence activities of the United Kingdom. It is authorized to investigate any person or movement that might threaten the nation's security.
    MI-5's earliest antecedent was a secret service formed in 1569 by Sir Francis Walsingham, who later became secretary of state to Elizabeth I. The need for centralized control of intelligence functions was first expressed early in the 20th century. MI-5 was formed in 1909 to identify and counter German spies then working in Britain, which it did with great effect. It was placed under the command of Vernon Kell, then a captain in the British army. ............