The anniversary was marked by a somber memorial ceremony at Hiroshima's Peace Memorial Park.
As the world takes a moment to reflect on that World War II tragedy, many are also thinking back to a more recent disaster -- the nuclear power plant meltdown at Fukushima.
Both events show that nuclear power is a dangerous force to reckon with. And although the incidents affected Japanese civilians in very different ways, the parallels are clear. As Japan struggles to define its approach to nuclear power post-Fukushima, today's Hiroshima anniversary serves as a poignant reminder of just how risky nuclear technology can be.
Old and New Catastrophes
Just after 8 a.m. on August 6, 1945, a U.S. Air Force B-29 bomber called the Enola Gay dropped a uranium bomb called 'Little Boy' on Hiroshima. The city was destroyed, and the blast -- along with the ensuing radiation -- killed an estimated 140,000 people.
Three days later, a plutonium bomb was dropped onto Nagasaki, killing up to 40,000 more. Japan surrendered within a week, bringing an end to World War II.
Monday's memorial ceremony took place in Hiroshima, not far from the spot where Little Boy touched down decades ago. Over 50,000 people attended the event. Visiting dignitaries from about 70 nations participated in a moment of silence, according to the Associated Press. Flowers were laid at the base of an eternal flame in the shadow of a stone monument.
It is quite likely that the Fukushima disaster was not far from the minds of the people in attendance. That event was occasioned by an earthquake and tsunami in March of last year, which resulted in a power loss at the Fukushima I Nuclear Power Plant, shutting down coolers and precipitating a meltdown of three reactors. Overheating and a series of explosions resulted in a radioactivity burst that immediately threatened everyone within a 12-mile radius.
It is difficult to estimate the number of fatalities and injuries caused by the Fukushima disaster, since radiation can take years to show effects. One Stanford University study found that the incident may result in a cancer epidemic that could kill up to 1,300 people. Furthermore, up to 600 people died in the evacuation following the meltdown -- but even this is tricky to tally since the quake and tsunami caused concurrent fatalities.
Following the disaster, anti-nuclear power activists were up in arms. They suddenly had record levels of public support; one 2012 poll found that 79.6 percent of Japanese residents surveyed were in favor of eventually phasing out nuclear power. And Japan did momentarily shut down about 50 plants in order to perform inspections and maintenance.
But keeping the plants closed would have been a tough sell -- nuclear plants provided about 26 percent of Japan's electricity in the year leading up to the disaster, according to Bloomberg. Shuttering all nuclear facilities would lead to a detrimental economic slowdown, with Japan doubling down to pursue cleaner energy infrastructure.
And so the closed plants are reopening -- and the people are protesting. On July 29, thousands of activists held a rally in front of the Diet, Japan's legislature. Demonstrations like these are becoming more and more popular with the general public.
"It is becoming a social movement to an extent that we did not initially anticipate," said one participant to Japanese newspaper Asahi Shimbun.
As a result of public resistance, the government has pushed back a major decision that could re-envision the country's energy policy, from August to September.
This all spells trouble for Japan's ruling party, the liberal Democratic Party of Japan led by Prime Minister Yoshihiko Noda. He was behind the recent restart of two major power plants, a move he considered necessary in order to avoid power grid blackouts. Elections are expected next year, and this could determine whether or not Japan will work to curb its reliance on nuclear power.
Most of those who protest the reopening of nuclear power plants in Japan are not old enough to remember the day that a nuclear bomb wiped out the city of Hiroshima, but the connection between the two events is still strong.
In fact, the word that has long been used to describe the survivors of Hiroshima -- hibakusha -- has also been applied to those who survived the Fukushima accident.
Akira Yamada, 86, told the Washington Post that he survived the devastation of Hiroshima before moving to Fukushima -- and today, he feels conflicted.
"Yes, the events are connected," he said. "With both, I have regrets."
He notes that when the Fukushima power plant opened, the city's economy suddenly flourished. At that time, Yamada saw nuclear power as a solution -- a way to turn the world's most deadly force into a useful resource. He knew many residents who depended on the plant to make a good living in Fukushima.
But when the plant spewed radiation that could still cause more than 1,000 fatalities, said Yamada, "I was in a difficult position."
And so is Japan as a whole.
Today, while Japan memorialized the victims of a World War II atom bomb, hundreds of people -- including hibakusha from both Hiroshima and Fukushima -- took to the streets to call attention to the nuclear power issue.
Prime Minster Noda did not waste the opportunity to bring up the Fukushima incident as he addressed the crowd at Hiroshima's Peace Memorial Park.
"As the only country to be victimized by an atomic bomb and experiencing its ravages, we have the noble responsibility to the human race and the future of the Earth to pass on the memories of this tragedy to the next generation," he said, according to Japan Times.
"Based on the fundamental principle of not relying on nuclear power, we will aim in the mid- to long term to establish an energy structure that will assure the safety of the people."