German combat troops are being stationed in France for the first time since the Second World War.
It is part of an effort to show the two EU powers have buried former hatreds.
A German battalion in a joint military brigade officially takes up arms at a ceremony in eastern France to be attended by the two countries' defence ministers.
French Defence Minister Alain Juppe told Germany's Sueddeutsche Zeitung newspaper that the presence of German soldiers in France is "highly symbolic" - and that "the wisdom of the leaders and peoples ended centuries of conflict".
The French-German Brigade was created in 1989. But until this year German combat troops had not been stationed in France, only French ones in Germany - a legacy of the allies' post-war occupation there.
German soldiers occupied France for more than four years after invading in 1940.