About 500 German soldiers were present when President Gauck delivered his address before the parliament building about the ultimately failed 1944 attempt on Hitler's life. The president remembered the soldiers who, 69 years ago on July 20, "didn't just obey orders, but thought critically and stood for their convictions in word and deed."

Also present were representatives of the federal and local governments and various clergy members.

The soldiers, Gauck said, "served the Federal Republic of Germany faithfully and bravely defended the rights and freedom of the German people."

Depicted in the American film "Valkyrie," starring Tom Cruise, the 1944 plot involved the assassination of Hitler and the arrest of the Nazi leadership. The plan was led by Colonel Claus Schenk Graf von Stauffenberg and by General Friedrich Obricht in his capacity as the head of the General Army Office. The idea was to make Hitler's death look like an SS coup d'etat rather than a military takeover.

The Führer's death was required to free Germans from their loyalty to him, or Reichswehreid, the historical oath of allegiance taken by soldiers following World War I and into the mid-1930s.

After the bomb intended to put an end to Hitler's reign detonated without achieving its objective, the soldiers involved in the conspiracy were executed by the Nazis.

'Not too late'

While Germany remembers mavericks, the Simon Wiesenthal Center has offered rewards for leads on the surviving Nazi death camp guards.

The Jerusalem-based director of the Nazi-hunting center, Efraim Zuroff, told the Westdeutsche Allgemeine Zeitung (WAZ) that he believed about 60 former Nazi death camp guards were still alive, "the majority in Germany." WAZ, published in the Ruhr District city of Essen, quoted Zuroff as saying 6,000 guards worked 70 years ago at camps where Hitler's regime murdered six million Jews across Europe.

Posters carrying the words "late, but not too late" will be displayed in Berlin, Hamburg and Cologne and shown in black and white the rail entrance to the notorious Birkenau camp, near Auschwitz, in formerly occupied Poland. Rewards worth up to 25,000 euros ($32,800) would be offered to informants.

Zuhoff said the center found encouragement by the May arrest of Hans Lipschis, a 93-year-old suspected former Auschwitz guard. A recent war crimes case against the 98-year-old officer Laszlo Csatary in Hungary after he fled to Canada following the war, for running a camp, where 12,000 Jews were sent to their deaths, in Kosice in present-day Slovakia.

Impetus for new investigations in Germany came in 2011 when a Munich court convicted the Ukrainian-born former Sobibor death camp guard John Demjanjuk. He died in March last year, aged 91.

mkg/kms (AFP, epd, dpa)