Leon was born to Jewish parents living near Tarnopol, then part of the Austro-Hungarian empire. During World War I, he was an officer in the Austrian army. Following his enlistment, Leon attended medical school in Vienna. After graduating in 1923, he opened a general medicine practice in Kolbuszowa, a town in south central Poland. He was one of the town's two physicians.
1933-39: Leon had never been active in Jewish affairs, but when the Germans deported Jews from their country in 1938, he felt compelled to do something. He organized a local relief committee and appealed to the Jews in town to contribute money. Just before the German invasion of Poland in September 1939, he was drafted into the Polish army and later captured by the Germans and imprisoned near Tarnow. Leon was released in December.
1940-42: Leon returned to Kolbuszowa and resumed his practice. When the Germans ordered the Jews to form a council, he was asked by the community to serve as its president. He accepted, reluctantly, hoping he could stand up to the Germans. When asked to provide a list of wealthy Jews whose homes they would loot, he gave only his name. When the Gestapo commandant demanded money to remodel Leon's house so he could live there, Leon answered defiantly, "If I can live in that house the way it is, you certainly can."
Leon and most of the Jewish council were arrested in late September 1942, and replaced with a new council. Leon was deported to Auschwitz, where he perished.