By Richard Lough and Luke Baker
PARIS (Reuters) - President Emmanuel Macron led tributes to the millions of soldiers who died during World War One on Sunday, holding a solemn ceremony attended by dozens of world leaders in Paris to commemorate the centenary of the Armistice.
U.S. President Donald Trump, Russian President Vladimir Putin, German Chancellor Angela Merkel and dozens of princes, monarchs, presidents and prime ministers joined Macron to mark the moment guns fell silent across Europe a century ago.
Those who fought in the trenches of World War One lived through an unimaginable hell, Macron said in a 20-minute address, highlighting that as well as the deaths of 10 million troops, millions of women were widowed and children orphaned.
"The lesson of the Great War can not be that of resentment between peoples, nor should the past be forgotten," said Macron, sorrow etched on the faces of former French soldiers standing to attention around him during the ceremony.
"It is our deeply rooted obligation to think of the future, and to consider what is essential."
The commemoration is the centrepiece of global tributes to honour those who perished during the 1914-18 war and to commemorate the signing of the Armistice that brought the fighting to an end at 11 a.m. on Nov 11, 1918.
In a glass canopy at the foot of the Arc de Triomphe, built by Emperor Napoleon in 1806, Trump, Merkel, Macron, Putin and the other leaders listened through earpieces as the French president spoke. Putin, who was last to arrive at the ceremony, gave Trump a brief thumb's up as he greeted them.
As Trump's convoy was making its way up the Champs Elysees to the Arc de Triomphe, a bare-breasted protester from the Femen radical feminist group ran towards his motorcade, coming within a few metres, before being apprehended by police.
Photographs of the incident appeared to show that she had the words "fake peacemaker" scrawled across her body.
"OLD DEMONS REAWAKENING"
In a rare public display of emotion by the leaders of two world powers, Macron and Merkel held hands on Saturday during a poignant ceremony in the Compiegne Forest, north of Paris, where French and German delegations signed the Armistice that ended the war.
The conflict was one of the bloodiest in history, reshaping Europe's politics and demographics. Peace, however, was short-lived and two decades later Nazi Germany invaded its neighbours.
Macron spent the week in the build up to Sunday's ceremony touring towns and former battlfields that laid along France's western front. During the tour, he warned of the dangers of the resurgence of nationalism in Europe, saying it posed a threat to the continent - a theme he touched on again in his speech.
"Patriotism is the exact opposite nationalism. Nationalism is its betrayal," the French leader said.
"Old demons are reawakening, ready to sow chaos and death," he said, warning of how ideology, religion and a disregard for facts could be exploited. "History sometimes threatens to repeat its tragic patterns, and undermine the legacy of peace we thought we had sealed with the blood of our ancestors."
After the ceremony, leaders returned to the Elysee Palace for a lunch to be hosted by Macron and his wife Brigitte.
On Sunday afternoon, Macron will host the inaugural Paris Peace Forum, which seeks to promote a multilateral approach to security and governance and ultimately avoid the errors that led to the outbreak of World War One.
Merkel said in a statement the forum showed that "today there is a will, and I say this on behalf of Germany with full conviction, to do everything to bring a more peaceful order to the world, even though we know we still have much work to do."
Trump, who champions a nationalist 'America first' policy, will not attend the forum but Putin is expected to.
(Additional reporting by Laurence Frost and Luke Baker in Paris and Joseph Nasr in Berlin; Editing by Laurence Frost)