When the 9.0-magnitude earthquake struck Japan at 2:46 p.m. local time on March 11, 2011, TIME photographer James Nachtwey was at home in Thailand. Within 48 hours, he traveled to Japan and made his way north of Sendai to Kesennuma, where he began documenting the catastrophe while under threat of possible nuclear contamination. Nachtwey describes what he saw: “The scale of this is beyond belief. Any one town would be a major disaster if it had been just one town that it happened to. It would be unbelievable. This happened to every town, from south of Sendai all the way to the northern end of Honshu. The entire coastline, town after town after town. It’s just apocalyptic. And it all happened between — what? How long did the actual wave [of the tsunami] take to come in and go out? Half an hour? It was just a very brief span of time. The ocean just destroyed — obliterated — a huge coastal area of Japan. Heavily populated. Every town is just wiped out. Flattened.”
You've got to see these pictures.