Answer:
Throughout the war, Wilm Hosenfeld likely saved the lives of 60 people, many of them Jewish. But without the pianist Władysław Szpilman, Hosenfeld might have been forgotten.
Hosenfeld died in a Soviet prison in 1952. By that time Leon Warm had already died, but his letter to Szpilman survived, and his sister wrote to Yad Vashem from Australia, confirming her brother's rescue.