With a tight grip on his flashlight, Tommy Cassoe looks like a Danish Indiana Jones as he crawls out of a bunker buried under the sand, one of 7,000 the Nazis built along Denmark's western shores to fend off an allied invasion.

"Mission accomplished. The bunker is empty," Cassoe exclaims, showing off his bounty on the Krylen beach to a crowd of onlookers: rusty cans, a plastic vial containing medicine in case of a mustard gas attack, and electrical cables.

This bunker and three others, entombed under the sand dunes of Houvig since 1945, were uncovered a few months ago in a violent storm, when giant waves swept away the sand, exposing glimpses of the cement and iron structures...