World leaders gathered in the driving rain in Paris on Sunday to mark 100 years since the end of World War I, with host Emmanuel Macron warning against nationalism at a time of growing strain between Europe and Donald Trump's America.
Around 70 leaders including US President Trump and his Russian counterpart Vladimir Putin marked the centenary of the 1918 Armistice in the French capital at 11am local time (1000 GMT).
After church bells rang out across France, the leaders sat together at the Tomb of the Unknown Soldier at the Arc de Triomphe for a memorial that included a performance by star cellist Yo-Yo Ma and the reading aloud of letters by WWI soldiers.
President Macron delivered a 20-minute speech that called on his fellow leaders not to forget the lessons of the past and worldwide hopes for peace.
"Ruining this hope with a fascination for isolation, violence or domination would be a mistake for which future generations would rightly find us responsible," President Macron told them.
He also delivered a stinging indictment of nationalism, calling it "the exact opposite" of the patriotism shown by soldiers.
"Nationalism is a betrayal," he said.
"By saying our interests come first and others don't matter we are erasing what makes a nation precious, what makes it live, what makes it great and most importantly of all, its moral values," he said, watched by President Trump, who prides himself on being called a nationalist.
The service concluded with the bugle call that was played at 11am on November 11, 1918 to signal the end of fighting on the Western Front.
Elsewhere, ceremonies in New Zealand, Australia, India, Hong Kong and Myanmar began a day of remembrance services around the world for a conflict that involved millions of troops from colonised countries in Asia and Africa.
The leaders of Commonwealth nations -- whose forces were deployed under British command 100 years ago -- also delivered messages of peace.
"This was a war in which India was not directly involved yet our soldiers fought world over, just for the cause of peace," Indian Prime Minister Narendra Modi said on Twitter.
"For our tomorrows, they gave their today," Australian Prime Minister Scott Morrison told people gathered at a ceremony in Canberra.
British Prime Minister Theresa May and Prince Charles, standing in for Queen Elizabeth, attended a separate remembrance event in London where thousands of well-wishers also paid their respects to fallen soldiers.
In Paris, German Chancellor Angela Merkel was due to give the opening address alongside UN Secretary General Antonio Guterres at a peace conference following the memorial service on the Champs-Elysees.
The Paris Peace Forum, conceived by Macron, is intended to highlight the importance of international institutions in helping resolve conflicts, avert wars and spread prosperity.
"The aim of the forum is to show that there are lots of forces in the international system -- states, NGOs, foundations, intellectuals, companies -- who believe we need a world of rules, an open world and a multilateral world," chief organiser Justin Vaisse told AFP.
Despite the show of unity at the Arc de Triomphe, tensions lurk beneath the surface.
President Trump, whose hardline nationalism has badly shaken the Western alliance, arrived in Paris on Friday criticising host President Macron for being "insulting".
President Trump took umbrage at a recent interview in which President Macron talked about the need for a European army and cited the US, along with Russia and China, as potential security risks.
During talks with President Trump Saturday President Macron said his remarks had been misinterpreted and that he was merely saying Europe needed to take greater ownership of its own security.
The "America First" leader, who faced criticism on Saturday for cancelling a trip to an American cemetery because of rainy weather, will snub the Peace Forum.
Other notable attendees of Sunday's Paris memorial service and Forum included Turkish President Recep Tayyip Erdogan, Canadian premier Justin Trudeau and Israel's Benyamin Netanyahu.
Despite maximum security in a city repeatedly targeted by jihadists since 2015, a protester from the radical feminist group Femen managed to jump over a barricade and got within metres of President Trump's motorcade as he made his way up the Champs-Elysees.
She was hauled away by security along with two others who were stopped on the edge of the famous avenue.
French Interior minister Christophe Castaner later said President Trump's security had "in no way been threatened".
About 70 current-day nations were involved in WWI, which had six empires and colonial powers at its heart: Austria-Hungary, Britain, France, Germany, Russia and the Ottoman Empire.
Around 10 million soldiers are estimated to have been killed during the fighting and more than double that number wounded.
Between five and 10 million civilians are estimated to have been killed.