Almost every kind of information can be relevant to intelligence, as becomes evident by reviewing the variety of intelligence outputs. Diplomacy requires information on the private opinions, negotiating positions, and political factors impinging upon actors with whom foreign relations are being conducted. This political intelligence may need to be supplemented by economic intelligence, which covers such areas as resources, national economic organization and strength, labor skills, industrial processes, long-term growth trends, foreign trade, balance of payments, and other information. Military intelligence is of key import and ranges beyond simple counting of numbers of men, ships, and planes. Naval and air intelligence may consider necessary information different from that needed by ground force experts. All will want material on foreign forces, but also predictions on how those forces may change in the future, and on the quality and flexibility of their support systems, weapons technology, trained manpower, planning processes, and the like. Filling in those blanks, in turn, requires more recourse to economic intelligence, as well as scientific and technical intelligence. The latter attempts to judge the capabilities of weapons by reference to data regarding scientific achievement, industrial base, research and development programs, general levels of technological sophistication, and other information.
Judgments in any of the particular intelligence fields may be influenced by additional kinds of information. These include biographical intelligence on the individuals who may be key actors in policies or programs in which intelligence may be interested. In addition, there is basic intelligence, which is a compendium of social, demographic, geographic, economic, and other data about societies of interest to the analyst.
There is also intelligence that is primarily about the adversary's own intelligence organizations and activities. A foreign nation, even a friendly country, may be of interest for the intelligence operations it conducts, the results achieved with a given style of organization, the threat it poses, some opportunity offered, some specific activity parallel to or interfering with friendly activities, or for many other reasons. In addition, separate intelligence requirements, collection, and analysis may be conducted for the precise purpose of carrying out an operation against a foreign intelligence service, most commonly in espionage or in attempts to recruit an agent.
The above represents a wide panoply of information that can be relevant, truly a world of secrets. The concept that so much raw information is required is a relatively recent development. In the United States, with arguably the most sophisticated approach to intelligence, the practice of closely meshing and piecing together huge arrays of information of many different kinds to derive knowledge on a single discrete question dates from only about World War II (1939–1945). At that time, benefiting from British (and other) experience, and building on a foundation of code breaking, the United States fashioned methods that relied upon several pillars of intelligence, representing different kinds of collection techniques. In the Cold War period and after, those techniques were successively improved and integrated, in a process that continues today. In contrast, prior to World War II, intelligence reporting remained episodic, focused on a single (or a few) sources, and did not explicitly aim at information for policymakers, except where given reports seemed to demand it.
A good example of crosscutting influences and the impact of different kinds of intelligence reporting is the history of U.S. intelligence on Soviet nuclear missile programs. In the period immediately after World War II, scientific, economic, and biographical data, along with intelligence sharing with British allies, enabled the United States to discover that the Soviet Union was pursuing creation of an atomic bomb. Predictions by U.S. military intelligence and the nascent CIA were not accurate on when the Soviets would acquire nuclear weapons, in part due to Soviet espionage, which reduced the technical uncertainties associated with the Soviet program. On the other hand, U.S. scientific intelligence in the form of atomic test monitoring aircraft provided instant knowledge that a nuclear test had been carried out in August 1949.
Predicting the rate at which the Soviets might manufacture nuclear weapons; their ability to deliver such weapons against the United States, either by bomber aircraft or by ballistic missiles; and the attendant production rates for those weapons became priority issues for U.S. intelligence. These concerns drove intelligence tasking and even technological research and development programs (especially those for the U-2 and SR-71 aircraft and the CORONA/Discoverer KH-4 photographic reconnaissance satellite) through the 1950s and even into the 1960s. The CIA sought to recruit agents for information in these same areas, and defectors leaving Russia, along with German scientists returning from working in Russia, were interrogated for their knowledge. Estimates of Soviet factory floor space, fissile materials availability, and other items were compiled from the intelligence and used to predict the size of the Soviet bomb and the delivery vehicle inventory.
In intelligence estimates between 1955 and 1960, the CIA successively overestimated Soviet bomber and missile forces. These estimates led to decisions by President Dwight D. Eisenhower to build up U.S. bomber and missile forces to very high levels, in fact levels that arguably led Soviet leaders in the 1960s to create land-and submarine-based missile forces far greater than required for basic security. Meanwhile, Eisenhower's confidence in his intelligence also led him to offer, at the Geneva Summit of 1955, an "Open Skies" plan for mutual verification of nuclear forces and confidence building, which Soviet leader Nikita S. Khrushchev rejected. In a negative impact of intelligence, in 1960 another Eisenhower-Khrushchev summit scheduled for Paris was aborted as a consequence of the shooting down of an American U-2 spy plane over the Soviet Union on 1 May 1960.
The planes and satellites provided U.S. intelligence with unprecedented information-gathering abilities. They served as platforms for high-resolution cameras to take pictures or for sensitive radio and electronic recording equipment to monitor radio communications or electronic emissions of all kinds. Even though Eisenhower prohibited further overflights of the Soviet Union after the U-2 was shot down, satellite capabilities soon replaced and outshone those of the aircraft. In this period, as John F. Kennedy took office as president in January 1961, the United States also enjoyed excellent data from a Russian agent, Colonel Oleg Penkovsky, an officer of the Soviet military intelligence with access to much highly secret information of interest to the CIA.
During the 1960s the arms race between U.S. and Russian missile forces continued to be the focus of the secret world of intelligence. This arms race was punctuated by the Cuban missile crisis of 1962. It was not until after the crisis that the Russians had a dependable ballistic missile capable of mass deployment in a protected mode. The Soviet Union began to build these missiles at an increasing rate. President Kennedy, who had discovered that the gap in missile strength actually favored the United States, relied upon this intelligence in canceling further U.S. production, capping the land-based missile forces at 1,052. The Soviets continued to deploy until they reached the figure of 1,512 in the early 1970s.
Predicting how quickly the Russians would increase their missile force, at what level they might curtail deployment, and whether they would also field novel technologies such as ballistic missile defenses or multiple independently targetable warheads became the key intelligence issues of the 1960s. The CIA and other agencies, even with the considerable intelligence gathered by their machine spies, underestimated the numbers of Soviet missiles in the long term (that is, beyond those under construction, which could be directly observed by reconnaissance satellites). On the other hand, the intelligence estimates did much better on predicting when the Russians would acquire new technologies. However, the estimates seem to have been less influential in the major weapons decisions made by the administration of President Lyndon B. Johnson, who initiated multiple warhead programs for both land-based (Minuteman III) and sea-based (Poseidon) missiles, as well as development of an advanced manned strategic aircraft (eventually the B-1 bomber).
Growth in Soviet strategic forces moved the United States to seek arms control negotiations with the Soviet Union. The Johnson administration concluded a nonproliferation treaty and other agreements prohibiting nuclear weapons on the seabed or in outer space. Johnson also attempted to open talks on strategic nuclear weapons, but the effort was canceled in August 1968, when the Soviets invaded Czechoslovakia. The administration of Richard M. Nixon followed up and actually began Strategic Arms Limitation Talks (SALT) in mid-1969, culminating in the SALT I agreement, signed on 26 May 1972. The course of those negotiations was influenced by diplomatic intelligence the United States picked up from Russian officials—in particular a technical collection program code-named "Gamma Guppy," in which the United States intercepted radiotelephone conversations among Russian leaders, as well as information gleaned directly from Russian negotiators. The intelligence estimates also gave the Nixon administration confidence that its negotiations covered relevant issues and that it had a handle on what Soviet strength would be under various possible outcomes. After the SALT I agreement, intelligence verified compliance, tracked technological developments, and assisted follow-up negotiations for SALT II and the two Strategic Arms Reduction Treaties (START I and START II), plus the Intermediate Range Nuclear Forces (INF) Treaty. Various intelligence disputes occurred in the 1970s and 1980s that affected these negotiations and U.S.–Soviet bilateral relations, but the essential point is that many types of intelligence reporting were relevant and that the intelligence had crosscutting influence.