The devastation and fallout also led to severe health problems for survivors and their children, and decimated civilian communities.

So, why exactly did the United States drop nuclear weapons on Japan? Well, in the years leading up to the bombing, World War Two was in full swing.  On one side were the Allies, consisting of the US, the UK, and a number of mostly European countries. On the other, were the Axis powers: Germany, Italy, and Japan.

The catalyst for direct confrontation between the US and Japan happened on December 7th, 1941.


At the time, Japan had begun advancing their fleet into the central and south-west Pacific, which included US territory in the Philippines. Japan intended to neutralize the threat of US force by bombing their Pacific Fleet at Pearl Harbor.

The surprise attack didn’t disable the US’s Navy, but it did immediately result in a formal declaration of war on Japan. Fast forward to 1945 Italy had already surrendered, and the Allies were invading the German capital. On April 30th, Adolf Hitler committed suicide, and by May, Germany surrendered.

But Japan refused to surrender and continued to fight, unabated.

Now with all eyes on Japan, the Allies needed to figure out how to end the war, and prevent further casualties. The first plan was to conduct an all out invasion of the Japanese mainland, in what was called “Operation Downfall”. However, Japan’s unique geography meant that there was really only one, predictable invasion entry point.

A preliminary study determined that as many as 280,000 people would die in the invasion.  In July, the Allies called for Japan to surrender, promising to bring “prompt and utter destruction” if they refused.


Japan ignored their request. Seemingly left with no better options, the decision was made by the US and the UK to drop the secret atomic bomb on one of Japan’s industrial and military strongholds, Hiroshima.

It was also noted by US officials that the bomb would be a significant display of power in post-war relations with the Soviet Union. On August 6th, 1945, a bomber plane dropped the 15 kiloton bomb, killing 30% of Hiroshima’s population, almost instantly. In the following days, the Allies again called for Japan’s surrender, warning of further destruction if they refused.

Japan did not respond.

But by early morning Moscow Time, on August 9th, the Soviet Union surprised Japan by declaring war, and invading a Japanese held-city. This shook Japanese officials, who did not expect the Soviets to violate their neutrality agreement. It also removed a huge assurance for Japan that the Allies would not be able to easily invade them by land.

Several hours later, the US dropped another atomic bomb, this time in Nagasaki, killing as many as 75,000 people. After six days of deliberations, Japan officially announced their unconditional surrender on August 15th, finally ending World War Two.


Today, the lasting effects of the bombings can still be seen throughout the two cities. Despite repairing the physical damage and rebuilding the relationship between the US and Japan, the events continue to weigh heavily in both countries histories. Over the past 70 years, the moral excuse for dropping nuclear weapons has been widely challenged and debated.