Denmark on Sunday marked the 70th anniversary of the escape of 7,300 Jews during World War II to prevent their deportation to a Nazi concentration camp.

At Copenhagen’s synagogue, Jewish community leader Finn Schwarz told several hundred people it was “almost a miracle” that the October 1943 operation in Nazi-occupied Denmark avoided the German patrol boats and managed to deliver the Jews to neutral Sweden.

Denmark’s Jews were to be deported to Poland, but a German official tipped off Danish lawmakers who told Jewish leaders.

481 elderly and sick Danish Jews who couldn’t get out were deported to a concentration camp in Czechoslovakia, where 53 of them died.

On Tuesday, a light show on the bridge connecting Denmark and Sweden will commemorate the escape.