A flooding provoked the largest evacuation ever mobilized in the Netherlands: 250,000 people were forced to flee their homes in Limburg and Gelderland.

Fifty years after World War II, something like the blitzkrieg returned to Nijmegen last week. Dutch soldiers swarmed around the city as low-flying helicopters thundered overhead. The scenes reflected the kind of combat the Dutch know best: struggling with the elements as an onslaught of water threatened to submerge vast…