When did the Cold War begin?

We all know when the Cold War ended: with the fall of the Berlin wall in November 1989.  When it began is much more controversial.  In my new book, Six Months in 1945, I say that it began in the six month period between the Yalta conference in February 1945 and the bombing of Hiroshima in August 1945.  I also argue that it was the inevitable outgrowth of World War II.  When Americans and Russians met in the heart of Europe in April 1945, they turned, almost overnight, from World War II allies into Cold War rivals.

For more on my reasoning, and why I differ with other historians, see an article that I just wrote for the History News Network.  And, of course, read my book!