Unknown people damaged the unguarded Hürtgenwald memorial in the Eifel.
The police in Düren announced on Tuesday that they had taken an exhibition board from the wall and tore down another.
Hürtenwald - The attack was noticed by the administrator of the memorial on Saturday evening.
There was property damage running into four figures.
The memorial commemorates a battle at the end of World War II in which thousands of US and German soldiers died.
There are several memorial sites, including military cemeteries.
The police asked witnesses for clues.
dpa