“The ocean will take it all. We won’t have a choice,” she said from her small stone house in Ste.-Marie-du-Mont, surrounded by rose bushes and mementos of a long life — including a knee-high shell casing, which she now uses to store scrap paper.

Ms. Dumont was a young teenager on D-Day, and vividly remembers the sound of planes overhead, bomb blasts, gunfire. Her father, a dairy farmer, dug a trench next to the house, where the family spent their nights praying for two weeks. “The bombing never stopped. It didn’t last just one day,” she said.

She watched in awe as columns of soldiers arrived, first on foot, but quickly followed by tanks, jeeps, bulldozers. That first day, 23,000 soldiers, 1,700 vehicles and 1,800 tons of supplies were delivered to Utah Beach. They were followed by nearly half of the U.S. troops heading to the front — more than 800,000 soldiers — and all the supplies to support them, over the next few months.

“People need to understand what happened here,” she said.

Farther east, a different conversation is unfolding at the Juno Beach Center — a museum set where 14,000 Canadian soldiers landed on D-Day. The beach here has actually thickened over the years, its dune consuming old German bunkers.