On 7 December, 1941, Japan attacked the American fleet at Pearl Harbor, Hawaii. Because the Americans were taken by surprise, 19 ships were sunk and about 2400 American soldiers and sailors were killed. Four years later, on 6 August, 1945, at precisely 8.15am, the first atomic bomb to be used in anger¹, exploded over the city of Hiroshima. The attack on Pearl Harbor four years earlier was one of the justifications President Truman gave for his decision to use the nuclear weapon. Over 240,000 Japanese civilians died - Pearl Harbor's devastation had been recreated 100 times over. The bomb dropped on Hiroshima, which was quickly followed by a second bomb dropped on Nagasaki three days later, forced Japan into a quick surrender.

Many factors contributed to the final decision to use the bomb. The traditional belief that dominated the 1950s and '60s - put forth by President Harry Truman and Secretary of War Henry Stimson - was that the dropping of the atomic bombs was a solely military action that saved as many as a million lives from the upcoming invasion of Kyushu².

In the 1960s a second view developed that claimed the dropping of the bomb was a diplomatic manoeuvre aimed at gaining the upper hand in relations with the USSR.

Today, 50 years after the two bombings, and with the advantage of historical hindsight and new evidence, a third view has been added. The decision to drop the bomb was made because of many domestic and international pressures and concerns. For instance David H Frisch, a scientist working on the Manhattan Project, noted: 'It was very important to prove the bomb a successful weapon, thus justifying its great cost.' Also, it could be considered that the sheer momentum of the project carried it through to completion. The initial target was Germany, who, it was thought, were on the brink of producing their own atomic bomb. With the fall of Nazi Germany, however, the target was shifted to Japan without even a break in stride. However, because the alternatives were never fully explored, one can only speculate about whether or not Truman's decision to drop the bomb actually saved lives and if the decision was a morally correct one.

Events Leading up to the Bombing

The war in Asia had its roots in the early 1930s. Japan had expansionist aims in Eastern Asia and the Western Pacific, especially in Indochina. The United States placed an embargo on materials, including oil, exported to Japan in the hope of curbing Japanese expansionism. Tensions still remained high in Asia, though, and increased even further in 1939 when Germany ignited World War II with an invasion of Poland. America's determination to remain isolated changed abruptly following Japan's surprise attack on Pearl Harbor on 7 December, 1941. In accordance with an agreement forged between President Roosevelt and British Prime Minister Winston Churchill, military strategists and politicians poured the majority of America's resources into the European theatre, and before the United States could fully mobilise, most of South-East Asia, including the Philippines, had fallen to Japan. Slowly, the United States recaptured many of the small islands that had been invaded by Japan, including Guadalcanal, Bougainville, Tarawa, Saipan, Iwo Jima and Okinawa.

Under the guidance of President Roosevelt, a top-secret joint effort between America and the United Kingdom was begun to build an atomic bomb that could be used against Germany. Run by General Leslie R Groves at locations such as Los Alamos, New Mexico, this programme was known only to a handful of scientists and politicians. Truman only learned of the project (then known by its code name S-1 and later as the Manhattan Project) from Secretary of War Stimson on becoming President on 25 April, 1945.

Both Japan and America were making preparations for a final end-all conflict, which both sides expected would involve an American invasion of mainland Japan. The Americans expanded conventional bombing and tightened their increasingly successful naval blockade. The Japanese began the stockpiling of aircraft, gathered a giant conscripted military force, and created an extensive civilian army that swore total, fanatical allegiance to the emperor.

In the end, these final preparations were never put to use. On 6 August, 1945, the American B-29 bomber Enola Gay, dropped the 'Little Boy' uranium atomic bomb on the city of Hiroshima. Three days later a second bomb, using plutonium and nicknamed 'Fat Man' was dropped on the city of Nagasaki by another B-29 called Bock's Car. On 14 August, the Japanese surrendered unconditionally and the war in Asia came to an end.

Pressures to Drop the Bomb

Truman's decision to drop these bombs was born out of a complex background. Pressure to drop the bomb stemmed from three major categories: military, domestic and diplomatic.

Military Pressures

The military pressures came from discussions and meetings Truman held with Secretary of War Stimson, Army Chief of Staff General George Marshal, Chief of Staff Admiral William Leahy, Secretary of the Navy James Forrestal and others. On 18 June, 1945, General Marshall and Secretary of War Stimson convinced Truman to set the date for an invasion of the island of Kyushu for November 1945.

Truman knew of the ferocious fighting currently taking place in the Pacific and naturally had a desire to minimize what he felt would inevitably be a long and bloody struggle. Truman, Stimson, and others, all believed the invasion of the Japanese mainland would be extremely costly, and therefore embraced the bomb as a military weapon whose use should be fully condoned and never questioned.

However, as Truman wrote in his diary, after the test in the New Mexico desert:

I have told the Secretary of War, Mr Stimson, to use it so that military objectives and soldiers and sailors are the target and not women and children.

He also wrote:

The atomic bomb seems to be the most terrible thing ever discovered, but it can be made the most useful.

It should also be noted that the targets were originally chosen with this in mind. Hiroshima was a major military staging point, with a convoy staging area, army headquarters, railway sidings and an industrial port. The second bomb to be dropped over Japan was not actually detonated over its the initial target. Kokura arsenal, the primary target, was covered by cloud when the aircraft arrived overhead, the pilot chose the only secondary target within range, the city of Nagasaki³.

Domestic Pressures

The second major source of pressure on Truman and his advisors to drop the atomic bombs came from domestic tensions and issues of re-election, along with a collective American feeling of hatred towards the Japanese race. Like most major military conflicts, there was an effort to establish the Americans as morally and socially superior to the Japanese. Truman was no exception to this generalisation, and on 25 July, 1945, he wrote that the Japanese people were, 'savages, ruthless, merciless and fanatical'. He knew that if he backed down and did not remain firm on his stance with Japan, the American public would be outraged. Furthermore, if the bomb was not dropped, Truman feared that it would prove extremely difficult in post-war America to justify the two billion dollars spent on the Manhattan Project.

Also, Truman became president because Roosevelt died while in office, and although he never fully embraced the idea of being President, a desire to ensure the possibility of his re-election would certainly have been at least a minor issue for him.

Diplomatic Pressures

The third major source of pressure on Truman to drop the bomb was diplomatic tensions with the USSR. Today, nothing is more debated by historians than whether diplomatic tensions played a role in Truman's decision. Truman's predecessor, Franklin D Roosevelt, followed a programme of cooperation and good relations with the USSR; however, Truman adopted a 'hardline' policy in which these generally good relations were abandoned.

While preparing for his first meeting with a Russian official as President of the United States, Truman exclaimed that if the Russians did not wish to be cooperative, 'they could go to hell'. Because of this new attitude, Truman undoubtedly wanted to end the war quickly and gain a foothold in the Far East before the Soviets could start to throw their weight around.

Alternatives to the Bomb

In hindsight it appears as if there existed several major alternatives to the dropping of the atomic bombs:

• A non-combat demonstration of the power of the nuclear bomb - One of the common misconceptions for why this alternative was never implemented was that there were no spare bombs. In actual fact, a fourth 'Fatman' type weapon was available on 13 August, 1945, and could theoretically have been dropped within a week of being deployed. Three more bombs were available by the end of September, and by the end of the year the Americans had a total of seven atomic weapons in their arsenal.

  This choice was actually ignored because a 'dry-run' was considered to be insufficient to force the 'fanatical' Japanese to surrender. The question must also be asked whether such a test would be sufficient to impress the Soviet Union, if indeed this was part of the considerations.

• A modification of the demand for unconditional surrender - America was awaiting Soviet entry into the war, and continuing conventional warfare - aerial bombing of cities and naval blockades - but could Truman afford to wait for the Soviets, or was he already considering the political situation of the Pacific Rim for the post-war years?

Finally however, Truman chose to discard these alternatives and dropped the bomb instead.

Conclusion

Truman became President only weeks before making this monumental decision; one can probably never know exactly why he finally decided to use the bomb, but it should be considered that during the Second World War, the ethics of fighting a war were completely different from what is now thought 'right and proper'. All of the major powers had been carpet-bombing cities for years. Centres of population were considered legitimate targets, and 'precision strikes' were decades in the future.

The final question on whether it was right or wrong to use the bomb in such a way is a moot one. The decision taken, was considered to be right by the people involved. Now of course, with hindsight, we can question that decision, but who can confidently say how things would have turned out if the decision had been different?

Related BBC Links

• Listen to an eyewitness account of the bombing of Hiroshima.

• Hear the memories of Harold Agnew, the bomb scientist who flew in the back-up plane in the bombing of Hiroshima.