August 6, 1945 . . . a B-29 bomber carrying a single weapon changed, perhaps forever, the way we think about war and peace. Sixty years ago, the United States became the first - and so far only - nation to use an atomic bomb against an enemy.
"It was a sight that really defied description," recalls Paul Tibbets, who flew the plane that dropped the atom bomb, "because of the fact that where there had been a city, there was nothing there but something that appeared to be a big, black, boiling mass."
In an instant, the Japanese city of Hiroshima all but vanished in a fiery blast hotter than the core of the sun. "My immediate thought was that if we are successful in the deployment of this weapon, there's nobody in the world who can stand up to it and we will see an end to this war," says Paul Tibbets. "It is the principle that we wanted to save lives. And I've had Japanese since [the end of World War II] tell me that we saved their lives, too, because the invasion would have been nothing but bloodshed. It would have been terrible."
According to political scientist Kenneth Waltz of Columbia University, most U.S. war planners feared that an island-by-island invasion of Japan could take months and cost a million allied lives.
"In taking Okinawa, 200,000 people were killed," says Professor Waltz. "That was a quarter of the population of Okinawa. So if the Japanese had accepted 200,000 deaths in Okinawa and 100,000 deaths by firebombing in Tokyo without surrendering, what were we to do?"
On August 9, 1945, three days after the atomic bombing of Hiroshima, the Japanese city of Nagasaki was destroyed in a second nuclear blast. Estimates vary widely, but at least 115,000 people were killed instantly and another 100,000 were injured by the two bombs that ended World War II.
Soon, what defense analysts often called "the winning weapon" became the centerpiece of American military strategy as a deterrent to a conventional attack against Western Europe by the Soviet Union. But with the development of Moscow's atomic arsenal, the face of war changed.
"The discovery of how to release nuclear energy has basically put an end to world-scale war," says historian Richard Rhodes, author of the Pulitzer Prize-winning book, The Making of the Atomic Bomb:
"It's remarkable, when you think about it," adds Mr. Rhodes, "that a nation as powerful as the United States was prepared to lose a war against a small, Third World country, North Vietnam, rather than risk using nuclear weapons when Vietnam was a client of a nuclear power, the Soviet Union. Clearly, something very different was going on than was going on during the First World War and the Second World War. And I think that difference had to do with the unacceptable risk of damage to an entire nation from these terribly destructive weapons."
Since the dawn of the nuclear age, Russia, China, India, Pakistan, France and the United Kingdom, as well as the United States, have built atomic arsenals. And there's near universal agreement among experts that Israel and North Korea also possess nuclear weapons.
But according to nuclear strategist and former U.S. arms control negotiator William Van Cleave, the politics of nuclear arms are just as important as the number of states that have them.
"Our general interest is in no further nuclear proliferation," says Mr. Van Cleave. "But having nuclear weapons does not make an enemy of a friend and not having them does not necessarily make a friend of an enemy. So we can't leave out the political factor. Nuclear weapons in the possession of the United Kingdom are not a threat to the United States. So it does matter who possesses nuclear weapons, for what purposes."
Many scholars warn that unlike during the Cold War, deterrence today may not prevent what could be the next use of these deadly weapons.
Although the possibility of a terrorist nuclear attack may be remote, Scott Sagan, Co-Director of the Center for International Security and Cooperation at Stanford University, notes that such an attack is difficult to prevent.
"You have to know against whom and where to retaliate for deterrence to have even a plausible chance of success," says Professor Sagan. "Secondly, a terrorist organization, which may well desire martyrdom or may feel that retaliation would create social revolution or anti-Americanism, may actually want retaliation. They certainly may not be deterred by it."
As the world enters what's often called a "second nuclear age", an era marked not by a superpower standoff, but by weapons proliferation and the threat of a rogue state or terrorist attack, many analysts say the United States should be prepared to use atomic weapons again, either in response to an attack or as part of a pre-emptive strike. Among them is nuclear strategist William Van Cleave.
"We have security interests abroad that need to be protected," says Mr. Van Cleave. We have U.S. forces abroad that need to be protected. We still need some weapons that are low yield, special effect -- the types that could destroy underground facilities for weapons of mass destruction without causing a lot of civilian deaths and destruction."
Nuclear weapons have been a mixed blessing. For six decades, they've been the greatest peacekeeping force the world has ever known.
But in sufficient numbers, their ability to destroy all life on our planet has made them the most dangerous weapons in history. And that, most observers say, is the best reason for peoples of the world to redouble their efforts in search of lasting peace.Perhaps that's the most enduring legacy of Hiroshima.
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