After the discovery of fission in Germany in 1938, scientists knew an atomic bomb was possible. Hitler’s Germany possessed a substantial quantity of scientific talent, had access to the necessary raw materials, and had the industrial capacity to produce an atomic bomb. Because of this, the American project essentially became a race to beat Hitler to the bomb.
When the Manhattan Project was in its infancy no specific targets were proposed for bombing, although Germany was understood to be the eventual recipient of an atomic attack. Specific target cities were not considered until the spring of 1945, shortly before the German surrender and just after Roosevelt’s death.
(Here is a link to primary source material on how and why the targets for the bombs were chosen.)
President Truman set up a committee to study the use of the bomb in combat. This committee, which was assisted by Oppenheimer and several other prominent scientists, concluded that the bomb should be used as quickly as possible and without warning. Regarding the final decision to use the bomb, Truman writes: “Let there be no mistake about it. I regarded the bomb as a military weapon and never had any doubt that it should be used. The top military advisors to the President recommended its use, and when I talked to [British Prime Minister Winston] Churchill he unhesitatingly told me that he favored the use of the atomic bomb if it might aid to end the war.” Harry S. Truman, Year of Decisions (New York: Doubleday, 1955), 419.
At its peak, the Manhattan Project employed approximately 129,000 individuals at several sites across the country (Los Alamos had about 5,000 people at the height of the war). This number included scientists, technicians, laborers, soldiers, and many other types of professionals with essential skills. At Los Alamos, Oppenheimer personally recruited the top scientific talent based on their experience and scientific expertise.
Perhaps the greatest legacy of Nagasaki and Hiroshima is that nuclear weapons have never been used again as weapons of war. Nagasaki and Hiroshima demonstrated the unprecedented destructive power of nuclear weapons and has deterred nuclear states from using these types of weapons in combat.
Consult Truman’s memoir (p. 420) and the Target Committee meeting minutes, which are available here: http://www.lanl.gov/history/atomicbomb/victory.shtml
Some associated with the Manhattan Project felt guilty but most, based on my knowledge, did not. Oppenheimer, for example, was regretful that children would be killed in the attacks but I don’t believe he ever questioned the necessity of the bombings. Many of the scientists were appalled by the destruction and campaigned against the use of atomic bombs in future conflicts but even among those, few regretted the decision to bomb Japan because the attacks ended the war.
I feel there are two things that are nearly certain: 1.) Japan would have ultimately been defeated, be it by blockade (resulting in famine and mass starvation), conventional bombing, full-scale invasion, or a combination of these tactics and, 2.) because the war would have continued for an indefinite period of time, more Americans would have been killed.
There are three basic types of WMD: nuclear, chemical, and biological. Chemical and biological weapons, in some form, have been used in combat for centuries, although twentieth century technology made these weapons a viable means of destroying large populations. As such, the only true weapon of mass destruction that has been originally devised since World War II is the hydrogen bomb. The United States tested its first hydrogen bomb, which had a yield of 10.4 megatons (MT), in late 1952. 10.4 MT is equivalent to nearly 700 Hiroshima-type (Little Boy) bombs or 500 Nagasaki-type (Fat Man) weapons.
Today, new types of nuclear weapons are not being developed by the United States. Rather, the challenge that modern atomic scientists face is preserving the aging nuclear weapons of the nation’s stockpile and preventing nuclear materials from falling into the hands of rogue states and terrorists. The technical portion of this work is done, primarily, at the country’s national laboratories.
The country’s national laboratories are run by subcontractors for the federal government. Los Alamos, for example, is a Department of Energy Laboratory that, until recently, was managed by the University of California. The current subcontractor that runs the Laboratory is Los Alamos National Security, LLC (LANS). LANS is a conglomerate primarily constituted of the University of California and Bechtel that was created exclusively for the purpose of running Los Alamos National Laboratory. Bechtel and other major defense contractors, such as Northrop Grumman, have often been selected to manage the Department of Energy’s nuclear facilities.
For the most part, I think that scientists and historians alike recognize Oppenheimer as a tremendous leader and a great thinker. Even before Oppenheimer came to Los Alamos, he was the leading American theoretical physicist and had played a prominent role in establishing the field in the United States. In some of his research, for example, he predicted the existence of black holes. Still, I think his work as an individual scientist is often overlooked (if not completely forgotten) in relation to the work that was done at Los Alamos.
In my opinion, Oppenheimer’s lasting legacy is twofold. First, he will be remembered as the man most responsible for bringing atomic bombs into existence. The paradox of nuclear weapons is that they’re incredibly destructive but, thus far, they have played an enormous role in preventing conflicts on the scale of the world wars. Oppenheimer’s name will always be intimately associated with these weapons and all the hopes and fears they have come to represent.
Second, Oppenheimer will be remembered as a political martyr. In 1954, the Atomic Energy Commission did not renew his security clearance largely (and unofficially) because Oppenheimer’s political enemies did not want him to have influence in the government. Oppenheimer was a liberal who, during the 1930s, associated with several members of the Communist Party. This was used against him during his security hearing in 1954, at the height of the Red Scare, and his years of loyal service to the government were disregarded. The poor treatment Oppenheimer received remains an example, to many, of how the power of federal officials can be abused to the detriment of the nation.
I really don’t think so. There have always been people; from clerics, to socialists, to journalists, to scientists, etc.; who have questioned the use of the atomic bombs in World War II, but the mainstream interpretation remains that the atomic bombs shortened the war, thus saving American and Japanese lives. Hiroshima and Nagasaki, for better or worse, represent the culmination of Oppenheimer’s work at Los Alamos and remain his greatest legacy. Although there will always be a revisionist challenge to the mainstream interpretation, I think history will continue to acknowledge Oppenheimer as a brilliant scientist whose leadership during the Manhattan Project led to the abrupt end of World War II and prevented another world war from occurring.