Manolis Glezos, a national Greek hero known for his act of bravery and defiance against the Nazi occupation during World War II, died on Monday. He was 97.

Glezos’ action was a rallying cry for the country’s resistance movement against the Nazi German occupation and emboldened Greeks during the difficult years of the war.

Revered across Greece’s political spectrum by left and right, Glezos was most famous for scaling the steep walls of the Acropolis with Apostolos Santos in 1941 to take down the swastika and replace it with the Greek flag.

Today, a plaque marks the spot where they climbed the walls on May 30, 1941.

It was the first visible act of resistance against the Nazis, who occupied Greece between 1941 and 1944.

Nazi authorities sentenced Glezos to death but never apprehended him.

Glezos died of heart failure at a central Athens hospital where he had been admitted on March 18.

Greek Prime Minister Kyriakos Mitsotakis led tributes to Glezos, calling him a “lionheart” and “the sweetest man.”

“The death of Manolis Glezos leaves Greeks poorer, but the legacy of his life leaves Greece richer,” he said in a statement.

“His example, that of a true patriot and fighter, is a guiding light for us all. And it gives us the strength to unite to overcome difficulties, like those we are experiencing today,” Mitsotakis said, referring to the coronavirus crisis.

Former left-wing Prime Minister Alexis Tsipras said: “He will live on through eternity as the symbol of a fighter who knew how to sacrifice himself for his fellow man.”

Glezos was a recognizable fixture in Greek politics and remained active throughout much of his life.