Nuclear Security Summit
SeongJoon Cho/Bloomberg
A man walks past a banner promoting the Nuclear Security Summit in Seoul, South Korea, on March 25, 2012. World leaders began gathering in Seoul for the two-day summit that begins March 26.
A man walks past a banner promoting the Nuclear Security Summit in Seoul, South Korea, on March 25, 2012. World leaders began gathering in Seoul for the two-day summit that begins March 26.