Solemn-faced, President Karolos Papoulias (c) looks...

Solemn-faced, President Karolos Papoulias (c) looks on during a memorial service for 318 people killed by Nazi troops on April 24, 1944, in the village of Pyrgoi, near Kozani in northern Greece. Papoulias, who lived in Germany for 15 years, said it is still difficult for many Germans to explain such atrocities, but that the country's new generation has overcome this 'burden' of the past. 'Peace is a prerequisite for progress and democracy. Peace cannot be imposed through war,' the president said during a brief speech at a lunch held in his honor after the memorial service.