ROME — For years, Gildo Negri visited schools to share his stories about blowing up bridges and cutting electrical wires to sabotage Nazis and fascists during World War II. In January, the 89-year-old made another visit, leaving his nursing home outside Milan to help students plant trees in honor of Italians deported to concentration camps.

But at the end of February, as Europe’s first outbreak of the coronavirus spread through Mr. Negri’s nursing home, it infected him, too.

Shut inside, he grew despondent about missing the usual parades and public speeches on Italy’s Liberation Day, grander this year to mark the 75th anniversary. But the virus canceled the April 25 commemorations. Mr. Negri died that night.

“The memory is vanishing, and the coronavirus is accelerating this process,” said Rita Magnani, who worked with Mr. Negri, at the local chapter of the National Association of Italian Partisans. “We are losing the people who can tell us in first person what happened. And it’s a shame, because when we lose the historical memory we lose ourselves.”

Time and its ravages have already cut down the lives and blurred the memories of a generation that saw close up the ideologies and crimes that turned Europe into a killing field.

The virus, which is so lethal to the old, has hastened the departure of these last witnesses and forced the cancellation of anniversary commemorations that offered a final chance to tell their stories to large audiences. It has also created an opportunity for rising political forces who seek to recast the history of the last century in order to play a greater role in remaking the present one.