On 6 August 1945, an American B29 bomber dropped the world's first deployed atomic bomb over Hiroshima. Three days later, Nagasaki was at the receiving end of a second American A-bomb. Why did America decide to hit Japan with two atomic bombs? Why were these two cities the targets? What were the implications for ending World War II and starting the Cold War? History Hit’s Rob Weinberg puts the big questions about this seminal event to Kevin Ruane, Professor of Modern History at Canterbury Christ Church University.