On this day in 1945, a US plane dropped the uranium bomb on the Japanese city of Hiroshima. Around 140,000 people were killed. Three days later, a second nuclear weapon was dropped on Nagasaki. Two weeks later Japan surrendered, ending World War 2. Today, bells have tolled in Hiroshimato to mark the 75th anniversary of the world's first dropping of an atomic bomb. Former US diplomat and now commentator, Brooks Spector reflects on the significance of that moment, its long-term impact, and what lessons have been learnt.