It wasn't only the lives of Jews that the Nazis stole, but their homes, businesses, jewellery, paintings and other personal artefacts. Jews forced to hastily flee for safety often sold off expensive works of art for a song. If there was no time, they left them behind.
For years, work has been going on to return paintings to families from whom they were stolen or extorted. In one of the most famous recent cases, the LA-based lawyer E. Randol Schoenberg helped Maria Altmann - who'd escaped from Nazi-occupied Vienna as a 21-year-old newlywed - recover five Gustav Klimt paintings, including the Viennese artist's shimmering, gold-encrusted portrait of her aunt, Adele Bloch-Bauer, in a Byzantine eight-year legal fight that took them to the US Supreme Court, and pit them against the Austrian and US governments.
The David and Goliath battle became the subject of a handful of "really detailed documentaries", Schoenberg tells me, which inevitably led to thoughts about a feature film. "People would say: 'Who would play you?' My sister used to call me Randy Brockovich," he says, laughing. "So people were talking about it and I figured I would put all the English-language materials together and write up what I thought were some of the important scenes, if there were to be a movie.'"
A spec script by Peter Woodward led nowhere. Later, though, the documentary Stealing Klimt aroused interest at the BBC, who optioned Schoenberg's story as a potential project. Now his and Altmann's struggle is about to reach multiplexes as Woman In Gold, directed by Simon Curtis, written by Alexi Kaye Campbell, and starring Helen Mirren and Ryan Reynolds. The movie is effectively a continuation of what wasn't just a fight for some valuable family heirlooms but, says Schoenberg, a "personal crusade to let people know the truth about what had happened to [Maria's] family, and what had happened to all of these Austrian Jewish families".
This sense of mission kept the pair going when all seemed lost. In fact, from the start the case had looked like an "impossible uphill battle", says Schoenberg. And no one, including him, thought they would win when it reached the Supreme Court. Even so, he told Altmann they should enjoy it. "Your story is going to be told," he said. "People are going to know. So whether we get the paintings back or not, we've at least accomplished something in telling the story."
It was his family's story, too, as his grandfathers, the Austrian composers Arnold Schoenberg and Eric Zeisl, had both been forced to find refuge abroad. ''My mother's parents left the day after Kristallnacht," Schoenberg says. "They were lucky to get out. Schoenberg became interested in genealogy when he was eight, and quickly became "aware of how lucky I was to exist". So, when Altmann, a family friend on his mother's side, asked for help in 1998, he couldn't resist.
She had been prompted by the passing of a new law in Austria designed to "return pictures that had been taken improperly and never returned, or pictures that had been actually returned but then were donated in exchange for export permits," says Schoenberg. He believes that the Austrians thought the Klimts would be exempted because Adele Bloch-Bauer had appeared to tell her husband Ferdinand to donate them to the nation in her will. However, he had been forced to leave without the paintings, following the annexation of Austria in 1938. When the Nazi government seized them, the decision was taken out of his hands.
By putting together documents held by Maria's family, Schoenberg built a case for their return but the Austrians resisted. When Schoenberg went to an advisory panel, he was excluded from the process. He considered suing in the Austrian court, but the filing fees were prohibitively high, even after being reduced.
Schoenberg discovered it was possible to sue a country in a case of property taken in violation of international law, if the country is engaged in commercial activity in the United States. The Belvedere, where the paintings hung, "sold books in the United States, it advertised tours, accepted US credit cards," he says. "So I thought we can maybe sue in the United States."
The Austrians appealed repeatedly, creating a war of attrition. Altmann was already in her 80s and it seemed they were hoping she would die before any resolution. "She was not the only heir but she was the last of her generation," says Schoenberg. "I think they realised the case would be less attractive to a judge if she wasn't around. So they thought it might go away." But they fought and won.
In June 2006, after the paintings were taken to America, the businessman Ronald Lauder bought the golden Adele Bloch-Bauer I from Altmann and the other heirs for approximately $135 million. The four other paintings sold for $192.9 million. A sixth Klimt painting, Portrait of Amelie Zuckerkandl, which appeared in an exhibition at the National Gallery in 2013, remains disputed.
Schoenberg, who poured much of his fee into a new building for the Los Angeles Museum of the Holocaust, of which he is president, believes that, for Altmann, who died in 2011 aged 94, actual closure came when the paintings were displayed in Los Angeles.
"We brought all five paintings back and they were shown in one room, just like they had been in Maria's uncle's home, and Maria and her family were all in this room with these paintings. For me, I had accomplished as a lawyer what we set out to do -which was to return these to her family."
