The definition of intelligence—the kind concerned with national security and practiced by national governments—has evolved dramatically over the decades. From Thomas Troy’s 1991 minimalist assertion that intelligence is simply "knowledge of the enemy," to the expansive, seventy-plus word definition found today on the website of the Office of the Director of National Intelligence (DNI), the field has matured both in scope and complexity, meeting the demands of the modern era by recognizing the wide array of threats and determining the purpose of intelligence.