Historian Frank Costigliola discusses the diaries of George F. Kennan, America’s most respected foreign policy thinker of the 20th century. His career included early postings in eastern Europe followed by Berlin in 1940–41 and Moscow in the last year of World War II. In 1946, the 42-year-old Kennan authored the “Long Telegram,” a 5,500-word indictment of the Kremlin that became mandatory reading in Washington. A year later, in an article in Foreign Affairs, he outlined “containment,” America’s guiding strategy in the Cold War. The Kennan Diaries, spans 88 years and totals over 8,000 pages, and is full of keen political and moral insights, philosophical ruminations, poetry, and vivid descriptions.