They tried to kill Hitler. Now they’re heroes.

Germany on Sunday honored a group of Nazi-era officers who tried to kill Adolf Hitler 70 years ago. The plot - portrayed in films such as the 2008 Hollywood movie "Valkyrie" - helped establish a principle under which German soldiers today are encouraged to defy orders if they would result in a crime or violate human dignity.

In a somber ceremony, President Joachim Gauck called the July 20, 1944, bombing of Hitler's Wolf's Lair headquarters in Eastern Prussia a "significant day in German history" for showing the world that there were Germans who opposed the Nazi regime.