Paris, France (BBN)-French President Francois Hollande and German Chancellor Angela Merkel are to mark the 100th anniversary of the battle of Verdun, the longest battle during World War One.
Hundreds of thousands of French and German soldiers died during 10 months of fighting in north-eastern France, reports BBC.
France eventually emerged victorious.
But today Verdun is seen as a symbol of Franco-German reconciliation, and Mr Hollande and Ms Merkel are expected to renew a call for European unity.
Speaking ahead of Sunday's commemorations, Ms Merkel said: "To be invited to these commemorations shows the extent to which relations between France and Germany are good today."
"Europe faces difficult tasks, there is no doubt about that," she said, in what was seen as a reference to the EU's continuing economic problems, its attempts to deal with a huge influx of migrants and sharp differences among individual states on the future of the 28-member bloc.
But Ms Merkel stressed that "Europe has also done and achieved many things".
The battle of Verdun, 21 February - 15 December 1916
Verdun - a strong point on the long front line dividing the French and German armies - was the longest battle of World War One
At the end of the bloodshed in December 1916, France won back nearly all the territory it had lost in February
General Erich von Falkenhayn, the Chief of the General Staff and Germany's principal strategist, targeted Verdun because of its position on the Allied line and its sentimental value to French people
Falkenhayn hoped to combine the Verdun offensive with a U-boat offensive against British shipping - the two campaigns together were designed to force France and Britain to seek peace terms
But Falkenhayn's plan for an attack that would economise on German resources failed to work out as he expected, and he used many more divisions than planned
Germany, like France, accumulated huge losses and gained little territory, leading it to throw more and more men into the conflict, and Verdun soon became a battle of prestige for the Germans, as well as the French
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