Donald Sheppard, a British veteran of World War II who landed on the beaches of Normandy during D-Day, helped liberate the Bergen-Belsen concentration camp and then spent his old age striving to keep the memory of his fellow soldiers’ sacrifices alive, died on Saturday in Basildon, Essex, England. He was 104.

His son, Jonathan, confirmed the death, at Basildon University Hospital.

Mr. Sheppard was one of more than 150,000 soldiers who crossed the English Channel on June 6, 1944. He landed at Juno Beach, in Normandy, under a hail of gunfire. More than 4,000 Allied troops died that day.

“When he landed on the beach, he said he was just walking over dead bodies,” his son said. “Dead boys, dead men. And they gave their life for our freedom. I think to him, personally, he never wants that to be forgotten.”

After his retirement, Mr. Sheppard devoted himself to keeping alive the memory of the soldiers who fought and died beside him. He raised money for veterans, made repeated trips to Normandy and, until recently, spoke to schoolchildren about the war.

“He always talked about the men — the boys, really — that didn’t come back,” his son said, adding, “He just felt so passionate about never forgetting.”