The new Oppenheimer movie has everyone asking questions about the atomic bombs dropped on Japan in 1945 - were two bombs necessary? Would the war have ended without it? Was there an ulterior motive? Would the Americans have dropped a third if they had it?

At the end of WWII, the Manhattan Project demonstrated the power humanity had harnessed for destruction. When the uranium bomb was dropped on Hiroshima on the 6th of August 1945, city residents saw a flash of light and a loud boom- virtually everything within a 2-mile radius was destroyed. Those who survived the initial impact were then caught in subsequent firestorms and after that, many succumbed to radiation poisoning. It's estimated 1 in 3 were killed. 3 days later, Nagasaki suffered the same fate.

At the time, it was said it was necessary to end the war and to show why these weapons should never be used again. But is that true? To answer some of the questions we've all been asking after learning about Oppenheimer, Dan is joined by Professor Paul Poast from the Department of Political Science at the University of Chicago who explains how the decision was really made to drop the bombs, what would have happened if they hadn't and reveals that the Manhattan Project was actually more about impressing Stalin than destroying Japan.

Produced by Mariana Des Forges and edited by Dougal Patmore.

Discover the past on History Hit with ad-free original podcasts and documentaries released weekly presented by world-renowned historians like Dan Snow, Suzannah Lipscomb, Lucy Worsley, Matt Lewis, Tristan Hughes and more. Get 50% off your first 3 months with code DANSNOW. Download the app or sign up here.

PLEASE VOTE NOW! for Dan Snow's History Hit in the British Podcast Awards Listener's Choice category here. Every vote counts, thank you!

We'd love to hear from you- what do you want to hear an episode on? You can email the podcast at [email protected].

You can take part in our listener survey here.