President Trump, British Prime Minister Theresa May and other world leaders gathered Wednesday on the south coast of England to mark the 75th anniversary of the D-Day landings, honoring the Allied forces who risked and gave their lives in the invasion that helped liberate Europe from Nazi Germany.

The Royal British Legion brought about 300 veterans, aged 91 to 101, to the ceremonies in Portsmouth, where many of the troops embarked for Normandy on June 5, 1944. After a flyover by the Royal Air Force and a salute from the Royal Navy, the veterans will return to the landing beaches overnight, just as they did 75 years ago.

"The Normandy landings 75 years ago were a moment of historic international cooperation," British Prime Minister Theresa May said. "And it is right that at the heart of today's commemorations are the veterans who fought to secure the liberty and the peace that we now enjoy."

The event, which kicks off two days of D-Day anniversary observances, is intended as a tribute to the troops who shaped history during the dangerous mission to reach beachheads and fight in German-occupied France.

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D-Day saw more than 150,000 Allied troops land on the beaches of Normandy in northwest France on June 6, 1944, carried by 7,000 boats. The Battle of Normandy, codenamed Operation Overlord, was a turning point in the war, and helped bring about Nazi Germany's defeat in May 1945.

Trump, in the ceremony at Portsmouth Wednesday, read an excerpt from a prayer that President Roosevelt said during a radio address on D-Day.

“Almighty God: Our sons, pride of our Nation, this day have set upon a mighty endeavor, a struggle to preserve our Republic, our religion, and our civilization, and to set free a suffering humanity," Trump said. "They will need Thy blessings. For the enemy is strong. He may hurl back our forces but we shall return again and again; and we know that by Thy grace, and by the righteousness of our cause, our sons will triumph."

Queen Elizabeth II, in her remarks, lauded the soldiers who participated in D-Day as "resilient."

“The fate of the world depended on their success," she said. "Many of them would never return and the heroism, courage and sacrifice of those who lost their lives will never be forgotten.”

Also among those who were in attendance Wednesday are presidents, prime ministers and other representatives of the countries that fought alongside the U.S. and Britain in Normandy: Canada, Australia, Belgium, the Czech Republic, Slovakia, Luxembourg, Denmark, France, Greece, the Netherlands, New Zealand, Norway and Poland.

The leader of the country that was the enemy in 1944, German Chancellor Angela Merkel, also attended.

Britain has promised "unprecedented commemorations" for today and tomorrow, involving testimony from veterans and military spectacle, including a flyby of 24 vintage and modern military aircraft.

In Portsmouth, dignitaries also plan to read from historical documents linked to D-Day. In May's case, it's a letter written by Capt. Norman Skinner of the Royal Army Service Corps to his wife, Gladys, on June 3, 1944, a few days before the invasion. It was in his pocket when he landed in Normandy.

"I can imagine you in the garden having tea with Janey and Anne getting ready to put them to bed," wrote Skinner, who was killed the day after D-Day. "Although I would give anything to be back with you, I have not yet had any wish at all to back down from the job we have to do."

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On Thursday the focus shifts to France, where commemorations will be held at simple military cemeteries near the Normandy beaches.

Some events were already held in France early Wednesday morning, with U.S. Army Rangers climbing the jagged cliffs of Normandy's Pointe du Hoc to honor the men who scaled them under fire 75 years ago.

Elderly veterans looked on as members of the 75th Ranger Regiment started mounting the limestone promontory at dawn, pulling themselves up on ropes one by one, seagulls swooping above.

They were recreating a journey taken by the U.S. Army's 2nd and 5th Ranger Battalions to destroy Nazi guns atop the cliffs. The operation helped prepare the way for Allied troops landing on beaches up a few miles up the coast.

Of the 235 men who took on the cliffs in 1944, only 90 were fit for battle two days later.

Elsewhere in Normandy, parachutists were jumping from C-47 transporters in World War II colors and other aircraft, aiming for fields of wild flowers on the outskirts of Carentan, one of the early objectives for Allied troops.

Among the jumpers will be American D-Day veteran Tom Rice, 97. He jumped into Normandy with thousands of other parachutists in 1944, and recalled it as "the worst jump I ever had."

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Like many other veterans, Rice said he remains troubled by the war.

"We did a lot of destruction, damage. And we chased the Germans out and coming back here is a matter of closure," he said. "You can close the issue now."

The Associated Press contributed to this report.