BRUSSELS (AP) -- At a site where their countrymen once slaughtered each other with machine guns, artillery and poison gas, the leaders of Britain, France, Germany and other European nations commemorated the 100th anniversary of World War I and vowed Thursday to preserve peace on the continent.
About half a million people died in the arduous battles in the flat, often muddy killing grounds in and around the small Belgian city of Ypres in western Flanders between 1914-18, one of the sites that reflected the savagery of what became known as "The Great War."
German Chancellor Angela Merkel said holding a summit of the 28-nation European Union in the city that had to be rebuilt from scratch after World War I sends a powerful signal.
"I believe this shows us again in which good times we live today, because the European Union exists and because we have learned from history," Merkel said.
World War I was unprecedented in scope and savagery: It claimed some 14 million lives -- 5 million civilians and 9 million soldiers -- including sailors and airmen from 28 countries, and left at least 7 million troops permanently disabled.
"We should remember those who served and why they fought ... and we should recognize that the peace we have today is something we should cherish every day," said British Prime Minister David Cameron.
Commemorating the war's 1914 start, the leaders walked through Ypres to the sound of drums to attend the "Last Post," a bugle salute to the fallen performed each evening at Menin Gate. The gate has been erected as a memorial on the main road where British and Commonwealth soldiers marched off to the front, many to never return.
Summit chairman Herman Van Rompuy urged EU leaders to act as "the guardians of vigilance" to prevent a reoccurrence of the folly that once engulfed the continent.
"It is our task -- in actions and words -- to prevent the spirals and exaggerations, to maintain trust, to preserve peace," he said in a speech that used four languages.
Despite the vows of "never again," the outcome of the conflict only sowed the bitter seeds that led to World War II and more slaughter. And the nationalist tensions that set off the killing never really died -- most recently resurfacing in Ukraine and Russia.
On Friday, EU leaders were planning to discuss the situation in Ukraine, which borders four EU countries and has been fighting a separatist insurgency in the east following Russia's annexation of its Crimean Peninsula. The leaders will talk with Ukrainian President Poroshenko and decide whether the bloc will impose further sanctions against Russia for its destabilizing actions in Ukraine.
Still, in a sign of how much most of Europe has changed since nationalism caused neighbors to go to war, those who gathered on the sidelines of the Ypres summit venue cheered when Merkel arrived. Breaching protocol, she was the only leader to walk toward residents, shaking hands and commenting on how nicely the town had been rebuilt.
"Thank you for hosting us," she told several people in the crowd.
Hours before the leaders arrived, 81-year-old Arthur Siggee and his wife Audrey, from Lincolnshire, England, were searching for a relative's name on the Menin Gate memorial. He carried a photo of his uncles, three brothers who all lost their lives in battles around the Somme area.
"This might be our last trip back, we are both in our 80s, so we can't do this much more," he said.
Over dinner at Ypres, the EU leaders went back to the business of running a bloc encompassing more than 500 million people and forming the world's largest economy. They were discussing a "strategic agenda," mapping out the bloc's policy priorities for the next five years.
On Friday in Brussels, they are also set to choose their candidate to head the next EU Commission, the bloc's powerful executive arm. That rancorous issue has pitted Britain against the majority of EU nations who support the former long-time prime minister of Luxembourg, Jean-Claude Juncker.
Separately, Irish Prime Minister Enda Kenny said the leaders had tentatively agreed to hold another summit July 17th to nominate a successor to the bloc's foreign policy chief, Catherine Ashton, whose term expires in the fall.
Virginia Mayo in Ypres, Belgium contributed reporting.
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