Open this photo in gallery Canadian World War II veteran Bill Tymchuk, looks at headstones after attending a ceremony at the Beny-sur-Mer Canadian War Cemetery in Reviers, Normandy, France. David Vincent/The Associated Press

The last time Arthur Boon stood on Southsea Common in Portsmouth, he was an 18-year-old Canadian infantryman getting ready to jump into a landing craft headed to Normandy for the D-Day invasion.

“We didn’t think we were going to go because all we thought we were doing was an exercise,” Mr. Boon, 94, recalled Wednesday as he looked out across the field and remembered the fateful morning of June 6, 1944. “You don’t know what’s going to happen. You don’t think you’re going to get killed. The only thing you think is ‘I hope this boat doesn’t get hit here, because I don’t swim very well and it’s too far to go back.' ” He paused and added: “Anybody who tells you they weren’t scared on D-Day, they weren’t on this planet. Because that fear is always there. It’s hard to explain.”

D-Day confidential: How four Canadian soldiers made it through their longest day

Postcards from the past: Remembering the Canadian soldiers who died in Normandy

Mr. Boon was among more than 300 D-Day veterans from Canada, the United States, Britain and a dozen other Allied countries who gathered on Southsea Common on Wednesday for a stirring ceremony to mark the 75th anniversary of the invasion. Most of the preparation for Operation Overlord, as D-Day was known, was done at Southwick House in Portsmouth, and the city’s open fields along the waterfront were key launching points. The veterans were joined by the Queen and a host of world leaders including Prime Minister Justin Trudeau, U.S. President Donald Trump, French President Emmanuel Macron and German Chancellor Angela Merkel.

Story continues below advertisement

The ceremony was broadcast on giant screens to thousands of people in a nearby park, cut off from the dignitaries for security reasons. It began with video messages from three veterans, including Canadian Bob Roberts, who was among the first soldiers to land on Juno beach that morning. “I was never brought up for killing people,” Mr. Roberts said in the video. “Thinking back now, I don’t know how I survived it.”

The event mixed singing, dancing and readings to tell the story of the buildup to D-Day, touching on everything from the roles of the soldiers, sailors and airmen to the fighters in the French resistance and the women who worked in factories building bombers. There was also a reading from the diary of a German soldier, which captured the terror he felt waiting for the onslaught he knew was coming.

One portion of the program covered the failed 1942 raid on Dieppe, France; of the almost 5,000 Canadian soldiers in the operation, 3,400 were killed, wounded or captured. The lessons learned from Dieppe proved critical to the planning of D-Day, which involved more than 130,000 ground troops, including 14,000 Canadians; 7,000 ships; and more than 14,000 aircraft missions.

Open this photo in gallery Justin Trudeau reads the Victoria Cross citation of Lieutenant-Colonel Cecil Merritt. POOL/REUTERS

Mr. Trudeau read a passage from the Victoria Cross citation for Lieutenant Colonel Cecil Merritt, who won the medal for his bravery at Dieppe. The citation noted how Lt. Col. Merritt led his unit’s advance through heavy shelling and how he kept fighting despite being wounded twice. “Waving his helmet, Lieutenant-Colonel Merritt rushed forward shouting ‘Come on over! There’s nothing to worry about here,’ ” Mr. Trudeau read from the citation.

Mr. Trump, Mr. Macron and British Prime Minister Theresa May also gave readings. Mr. Trump recited Franklin D. Roosevelt’s famous prayer, The Mighty Endeavor, which was delivered in a national radio broadcast the night of the invasion.

Mr. Macron read the last letter written by 16-year old Henri Fertet, a resistance fighter who was executed. The French President was also the only leader to veer off script. Before his reading, Mr. Macron offered his thanks to the veterans. Ms. May read a letter from Captain Norman Skinner to his family, which was found in his pocket after he died on Sword Beach on June 6. “My thoughts at this moment, in this lovely Saturday afternoon, are with you all now,” the letter said.

The Queen, who served as an army mechanic during the war, spoke about the resilience of the “wartime generation” and said that many people thought her attendance at the 60th anniversary of D-Day would be her last. “I am delighted to be with you in Portsmouth today,” she said. “It is with humility and pleasure, on behalf of the entire country – indeed the whole free world – that I say to you all, thank you.”

Story continues below advertisement

Near the close of the event, 99-year old British veteran John Jenkins walked on to the platform and offered a D-Day message to the veterans and those who died. “I was terrified, I think everyone was,” he said. “You never forget your comrades. We must never forget.”

After the service, Canadian veteran Bill Wilson talked about the frustration he felt about D-Day commemoration ceremonies. Mr. Wilson, 94, was an anti-aircraft gunner on a Canadian destroyer during the D-Day landing. “I think governments feel it’s important to recognize what happened, but the actual event? I don’t think it means anything to people,” he said sitting at a table and watching as Mr. Trudeau shook hands with several veterans. “I don’t think the current generation really cares. … This was an important contribution that Canada made, and Canadians just don’t understand.”

Mr. Wilson shook his head and mentioned a school classmate who died on D-Day moments after storming the beach. He said he plans to visit his friend’s grave in France when he heads to another ceremony in Normandy on Thursday. “They say these guys are heroes,” he added, pointing to the other veterans. “The heroes are buried over there [in France]. When those guys landed, they did so for a cause. They didn’t have to.”