Russia’s Old Bombs Elude Ukraine’s Modern Defenses

Maryna Ivanova, a young woman living in a riverside village in southern Ukraine, had an uneasy feeling when her fiancé and brother left for work one morning in early May. They were headed to a nearby island in the Dnipro River, the watery front line between Russian and Ukrainian forces, and the area was getting heavily shelled.

Standing at her stove, making pork and potato soup, Ms. Ivanova heard — and felt — an enormous blast, much more frightening, she said, than the explosions that have become routine.

“It felt...