Veterans are marking the 60th anniversary of one of World War II's bloodiest battles - at Monte Cassino.
Soldiers at Cassino fought for four months
The Duke of Kent is joining 300 British veterans for the service in Italy to mark the end of the battle, which claimed the lives of 200,000 soldiers.
Former soldiers from Poland, New Zealand, Canada and other countries will also be at Monday's service.
It took four months for Allied troops to dislodge a German rearguard from the hilltop near the town of Cassino.
In a series of battles Allied troops advancing on Rome attacked retreating German forces dug in at the abbey on top of the hill.
The BBC's David Willey in Cassino said the war graves of more than 4,000 British and Commonwealth servicemen stretched in every direction from the site.
He said: "You realise just what a slaughter it was.
"Some of the survivors have talked about fighting a World War I battle in the second world war.
"It really was one of the major events of the Italian campaign."
By the time the battle began in February 1944, Italy's fascist leader Benito Mussolini hadbeen ousted and Italy had switched sides but the Germans were doggedly resisting attempts by the Allies to drive them out.
This year's commemorations take place in the shadow of the reconstructed abbey, which was destroyed by Allied bombing.
It may be the last major battle anniversary attended by survivors, many of whom are now in their 80s or 90s.
British veteran Jack Reid was at Cassino on Monday on what was also his 80th birthday.
He told BBC Radio 4's Today programme he had turned 20 during the campaign.
"There's a big difference between today and yesterday, he said.
Mike Ashmore from Auckland, New Zealand, was representing his 84-year-old father, who was unable to join the country's delegation at the commemorations.
"It's very important that the second generation come and show their respect for what those veterans did," he said.
Author Matthew Parker, who interviewed veterans for his 2003 book Monte Cassino, said the battle had been overshadowed by the D-Day landings in Normandy, which remain the focus of Britain's war commemorations this year.
He said: "It's remembered with great bitterness by people who fought there. Not only because it was incredibly bloody and incredibly hard, but because it's really been forgotten by a lot of people."
Parker said conditions were grim, with some soldiers having to be to be carried down from the hilltop after their limbs seized up in the freezing temperatures.
He said: "Either you were in the soggy valleys in a foxhole filled with water or you were up in the mountains with the snowstorms.
"They can't actually describe it without breaking down in tears. It was an absolutely ghastly place."
Comic Spike Milligan fought at Monte Cassino before being evacuated as a psychiatric casualty after being wounded.
Parker said: "They [psychiatrists] found that all of the frontline soldiers were displaying symptoms, such as shaking, like the ones they were treating in the mental wards.
"Effectively the whole place had gone mad. I only met one person who wasn't wounded or didn't have some kind of psychological damage."