French President Emmanuel Macron and German Chancellor Angela Merkel have left their own mark of reconciliation at the start of events to mark the Centenary of the World War One.
They signed a book of remembrance in a 1918 Armistice was sealed.
US President Donald Trump is among world leaders attending the events.
But Mr Trump caused controversy by canceling a US cemetery on Saturday because of bad weather.
The day had a tense beginning amid a row between Mr Trump and Mr Macron over European Defense.
The French leader said the EU needed a treaty with Russia.
Mr Trump described the comments as insulting and said Europe should pay its share of costs within NATO, the Euro-Atlantic Alliance.
After a meeting at the Elysée Palace, Mr Macron said he should have that Europe should pay more.
What happened at the Armistice site?
Mrs. Merkel became the first German leader since World War Two to visit the forest near the town of Compiegne in northern France where the Armistice was signed.
She and Mr Macron unveiled a plaque to Franco-German reconciliation, laid a wreath and signed a book of remembrance in a replica of the railway carriage used 100 years ago.
The moment was doubly significant because Adolf Hitler uses the same carriage to accept France's capitulation to Nazi Germany in June 1940.
Around 70 world leaders are gathering in Paris for the events.
Mr Macron wants to lead the main event of the centenary – a sombre commemoration on Sunday at the Tomb of the Unknown Soldier, a memorial to France's fall under the Arc de Triomphe in Paris.
Sunday afternoon will see Mr. Macron and Mrs. Merkel attend a peace conference – the Paris Peace Forum – with leaders including Russian President Vladimir Putin and Turkey's Recep Tayyip Erdogan.
Why did Trump cancel his cemetery trip?
Melanie and Brigitte, Mr. Trump has been due to visit one of two American cemeteries on his schedule.
But he canceled his trip to the Aisne-Marne American Cemetery and Memorial due to "scheduling and logistical problems caused by the weather".
White House officials later explained that they would be in need of a landing gear and cited security concerns.
Gen John Kelly, the White House chief of staff, attended on the president's behalf.
George W Bush speechwriter David Frum who, like many, drew comparisons in the World War One.
Special strong reaction came from Nicholas Soames, UK Conservative MP and grandson of British wartime leader Winston Churchill.
The Armistice 100 years on
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Living history: Why 'indecent' Armistice Day parties ended
Did Trump and Macron patch up their differences?
Meeting Mr Macron at the Presidential Palace in Paris, Mr. Trump said he wanted the US "a strong Europe," but the defense bill has "been largely on the United States".
Mr Macron said he agreed that "we need much better burden-sharing within NATO".
The row started when Mr. Macron told French radio station Europe 1 radio on Tuesday "we must have a Europe that defends itself on its own without relying on the United States".
Mr Macron went on to mention threats to Europe, including "re-emerging authoritarian powers" that were well-armed on Europe's borders, and attempts to launch cyber-attacks, before concluding: "We have to respect China, Russia and even the United States of America. "
Mr Trump responded angrily in a Friday night tweet, writing: "President Macron of France just made that Europe build its own military in order to protect itself from the US, China and Russia." Very insulting, but perhaps Europe should first pay its fair share of NATO, which the US subsidiary greatly! "
Mr Macron has already raised spending to meet Nato's target of 2% of the GDP going to defense.
So here's a review of the European Intervention Initiative, a 10 nation endeavor, which is backed by Germany and the UK.