The devastating earthquake and tsunami that triggered a nuclear disaster in Japan a year ago on Sunday has cemented relations between the United States and Japan, President Obama said today.

Obama applauded the United States' quick response in sending the largest bilateral military operation ever -- including aircraft, Navy ships and disaster relief efforts -- to Japan in the days following the magnitude-9 earthquake and tsunami that devastated part on Japan on March 11, 2011.

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An occasional series looking at the political and policy - and literal - fallout from the 2011 nuclear disaster in Japan.

"One year later, we remain committed to assist the people of Japan to rebuild," Obama said. "This effort, led by the Japanese government, has benefited from the compassion of the American people, who in difficult economic times have given generously to help."

The temblor and tsunami that struck Japan's northeastern shore left more than 19,000 people dead or missing.

The international community began scrambling within days to respond to the crippled Fukushima Daiichi nuclear complex more than 130 miles north of Tokyo, where cooling systems were damaged or washed away and three of the six reactors experienced core meltdowns. Hydrogen explosions also ripped through the facility, and Tokyo Electric Power Co., the plant's operator, scrambled to halt radioactive leaks.

Due in part to those efforts, nuclear power is safer now, a year after the event, International Atomic Energy Agency (IAEA) Director-General Yukiya Amano said. Meaningful steps have been taken to strengthen global nuclear safety, and the world came to recognize the importance of having a strong, independent nuclear safety framework, he said.

"Nuclear safety is stronger than it was a year ago," Amano said in a statement. "Fukushima Daiichi was a very serious accident, but we know what went wrong and we have a clear course of action to tackle those causes -- not only in Japan, but anywhere in the world."

Still, Amano warned that the global nuclear community must keep up the focus on safety and that "complacency can kill."

The disaster was "a jolt" to the nuclear industry, regulators and governments that revealed "existing weaknesses of design regarding defense against natural hazards, regulatory oversight, accident management and emergency response that allowed it to unfold as it did," Amano said.

Japanese regulators were not sufficiently independent, allowing for weak oversight of TEPCO, and not enough attention was paid to extreme events that could cripple nuclear reactors, he said. Training to respond to such disasters was inadequate, and the order of command was unclear, he added.

"Human failings such as these are not unique to Japan," Amano said. "We humans learn from our mistakes. Countries around the world are searching out the weak links in their own systems and taking action to strengthen them."

IAEA has since taken steps to bolster nuclear safety around the world, including developing a new methodology for assessing the vulnerability of reactors, reinforcing its own safety standards for siting, designing and operating plants, and learning from the Fukushima accident.

But anti-nuclear groups like Greenpeace say the nuclear industry still needs to be reined in.

Jan Beránek, the head of Greenpeace's nuclear campaign, said no lessons appear to have been learned from Fukushima, international governments are not holding the industry accountable, and unless things fundamentally change, the next nuclear meltdown is inevitable.

"Industry and politicians around the world rushed to exercise the so-called stress tests only to conclude that no single reactor in the world is unsafe and needs to close," Beránek said in an email. "I have no doubt even Fukushima Daiichi itself would have passed those farce tests."

Although some nations, like Germany, Switzerland and Belgium, retreated from nuclear power in the weeks following Japan's crisis, the United States stood by the power source. The Obama administration stood firm behind developing nuclear technology within days of the accident and launched a national safety review of the country's 104 operating reactors.

Rust Deming, a former acting director of the State Department's Office of Japanese Affairs, said today at a lecture in Washington, D.C., that it remains to be seen whether the disaster will spell the end of nuclear power internationally. It's also unclear whether relations between the United States and Japan will continue to strengthen or whether the two countries will sink back into their narrow, domestic issues, he said. Deming is now an adjunct professor of Japan studies at Johns Hopkins University.

But Deming said nuclear power has to be part of the international energy mix as new reactor designs use passive safety systems to cool reactors without power during emergencies. Lessons learned from the Fukushima accident has the potential to bolster international nuclear safety, he added.

"Hopefully, this will push us in the right direction," Deming said.