The WWI commemorations come at a watershed moment for the liberal post-war order, with anti-immigration populists at the helm in the US and Brazil, sharing power in Italy, and making strong gains in Germany, where Merkel has announced her resignation in 2021 after a series of electoral setbacks.
Some 10,000 police have been drafted in to ensure maximum security in a city repeatedly targeted by jihadist.
The memorial is doubly symbolic as Adolf Hitler forced the French to return to it on June 22, 1940 to sign their own surrender at the start of World War II.
The German chancellor will be first to speak Sunday afternoon at a Forum for Peace which Macron hopes will help foster multilateralism. Putin is expected to attend, Trump is not.