VIENNA: A vibrant city of poets, artists and thinkers in the early 1900s, it went down in a sea of swastikas after Hitler's triumphant return: Vienna after the Anschluss lost not only many of its people, but a great deal of its talent.

On March 12, 1938, Nazi troops marched into Austria. Three days later, Austrian-born Adolf Hitler gave a rousing speech from the balcony of Vienna's Imperial Palace to a jubilant crowd of 250,000 and Austria ceased to exist as an independent state.

An exodus that began years earlier when the Nazis took power in Germany accelerated.

And in the process, Austria lost many of its biggest names: people like Sigmund Freud and Oskar Kokoschka, and future luminaries such as Oscar-winner Billy Wilder and Carl Djerassi, who would develop the contraceptive pill.

"(It was) a monstrous cultural blow," says Johanna Rachinger, director of Austria's National Library (OeNB), which retraces the fateful days of March 1938 through photographs and testimonies in a new exhibit entitled "Night over Austria".

Post-war chancellor Leopold Figl once noted that: "Austria gave away the most Nobel prize winners, proportionally to the rest of the world".

Among these were earlier Nobel laureates Erwin Schroedinger (Physics, 1933) and Victor Hess (Physics, 1936) but also future honorees -- like Elias Canetti (Literature, 1981), Walter Kohn (Chemistry, 1998) and Eric Kandel (Physiology & Medicine, 2000) -- who fled Vienna after the Nazis' arrival and achieved success abroad, often after changing their nationality.

"The effect was a provincialisation of Austria's scientific landscape after 1945," says historian Johannes Feichtinger from the Austrian Academy of Sciences (OeAW).

"The country's most brilliant minds were expelled... In the post-war period, universities were in many cases dominated by mediocre figures, including people who owed their career to the Nazi regime," he told AFP.

A dynamic film industry was also choked as restrictions were imposed by the Nazi regime and Jewish artists fled to Hollywood.

Austria has only recently regained cinematic success -- thanks to people like Michael Haneke or Christoph Waltz -- but the local press has repeatedly pointed out that most of the country's Oscars have been won by exiled filmmakers.

The list of talent that left Austria behind includes actor Peter Lorre, novelist Stefan Zweig, photographer Erich Lessing, Fritz Lang -- the director of "M" and "Metropolis" -- and Billy Wilder, who created classics such as "Some Like It Hot" and "The Apartment".

"There was a great bloodletting of culture and intellect," Marcus Patka, curator at the Jewish Museum Vienna, told AFP.

"In 1933, many intellectuals and artists -- Jews and non-Jews -- had fled from Germany to Vienna.

"They were again displaced (in 1938) and the problem is that after the war, very very few of these people came back," he said.

Already before the Nazis' power grab, a lack of serious funding in Austrian scientific institutions and rampant anti-Semitism in academic circles led many leading scientists to seek their fortune abroad, according to Feichtinger.

"Scientists didn't have the opportunities in Austria to make careers as they later did in the United States," he said, in reference to many of the later Nobel laureates who benefitted from well-funded US facilities to conduct their research.

With the Anschluss however, the situation worsened overnight: within days, scientists and artists with Jewish backgrounds or dissenting political ideas were shut out of universities and jobs.

The debate over Austria's role in the annexation -- was it a victim or a collaborator? -- has raged for decades.

In a referendum on April 10, 1938, 99.73 percent of Austrians voted to join the German Reich.

A month earlier however, chancellor Kurt Schuschnigg had still called for a free and independent Austria.

Under pressure from Hitler and with Nazi troops at the border, he resigned on March 11, proclaiming that the country "renounces the use of violence". Mexico was the only country to formally protest the annexation.

For the 75th anniversary of the Anschluss, Austrian President Heinz Fischer will take part in a series of commemorations, including the laying of a wreath at the city's memorial against fascism.