Before the British invented the Enigma decoding device and began reading the other fellow's mail, the term intelligence—at the national level—called up a different idea than it does today. Earlier practitioners of intelligence sought to see the world through the eyes of their adversaries and international competitors, and understand their problems, opportunities, and pressures with sufficient fidelity to anticipate their moves.
The great practitioners could advise their statesmen of initiatives to shape or frustrate their adversary's actions in useful fashion. Their product was a shrewd appraisal of his goals and strategy and his likely reaction to initiatives being contemplated against him. Further, they knew an adversary's culture intimately, and their anticipations of his actions often were based on a steady stream of information, much—but not all—of which came from unclassified, open sources. Intelligence in this sense was inherently strategic and long term: the endless chess match among national leaders called the "Great Game." Although uncertain at times, it was correct often enough that it was the most important type of knowledge that leaders could hope to have.