When a huge earthquake and tsunami struck Japan on March 11, 2011, devastating towns and triggering nuclear meltdowns in Fukushima Prefecture, a stunned world watched the chaotic struggle to contain the world's worst nuclear disaster since Chernobyl.

An onslaught of waves sparked by the 9.0 magnitude quake crashed into the country's northeastern coast, killing nearly 20,000 people and crippling the Fukushima No. 1 plant. More than 160,000 residents fled as radiation spewed into the air.

At the time, some — including then-Prime Minister Naoto Kan — feared Tokyo would need to be evacuated, or worse.