Daniel, usually known as Danek, was one of three children born to Raphael and Amalia Schwarzwald, a Jewish couple living in a village near Lvov. When he was a young boy, his family moved to Lvov, where he went on to attend secondary school and a business college. Daniel opened a lumber export business. He traveled extensively and could speak Polish, German, Russian, Yiddish and English.

1933-39: Business prospered and in 1935 Daniel married Laura Litwak and settled in an apartment in a Christian section of Lvov. But war loomed and industrial Lvov was coveted by both the Germans and Soviets. Daniel wanted to emigrate to Britain, where he had business contacts. But his wife, who was pregnant, did not want to abandon her parents. In September 1939 the Soviets occupied Lvov and Daniel's business was expropriated.