While the reality of intelligence gathering isn't always as thrilling as popular spy novels and films make it seem, modern intelligence gathering operations are ample and a crucial part of diplomacy and military operations. This in-depth guide covers the nature and intriguing history of intelligence gathering. The types and sources of intelligence are presented thoroughly alongside important historical examples of spy operations or technologies used in the spy game. The text also provides a comprehensive guide to the world's most notable national intelligence systems, including those of the United States, the United Kingdom, and Russia.