Testimonies written by soldiers on the day the ceasefire took place, and one by a Chinese laborer serving the Allied Forces in Normandy, were read by high school students at Sunday's event.

On Saturday, Macron and Merkel joined hands and signed a book of remembrance in a railway carriage identical to the one where the 1918 Armistice was inked in the Compiegne Forest, north of Paris. The two leaders also unveiled a plaque to Franco-German reconciliation and laid a wreath.

On Sunday afternoon, Macron was scheduled to host the inaugural Paris Peace Forum, which aims to promote a multilateral approach to security and governance and avoid the horrible errors that led to the outbreak of WWI.

Trump, whose nationalist "America first" policy is at odds with Macron's philosophy, planned to skip the forum.

In a statement, Merkel said 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."

Other commemoration events were held in Europe and across the world on Sunday.

Shen Dingli, a professor of international studies with Shanghai-based Fudan University, noted that WWI was not intended but triggered by an incident. "Today's world is full of turbulence. Though nations often compete normally and constructively, such interaction could go weird," he said.

"Without proper communication and mutual understanding, conflict could arise and escalate, potentially leading to a major disaster."