No one has exact figures but the American Association of Museums says that millions of artworks and cultural artefacts were confiscated, stolen or appropriated under duress by the Nazis.

The right kind of art
The Nazi obsession with art began to take shape soon after Hitler came to power. He viewed Germany's Weimar republic of 1924-1930 as a degenerate period and, in 1933, he ordered the closure of art schools that displeased him. Cubist, impressionist and expressionist art was purged from public places and museums were encouraged to exhibit "pure" forms of art that celebrated the great German people. Any pieces by Jewish artists were purged.

The plunder begins
After Germany absorbed Austria into the Third Reich under the Anschluss of 1938, Nazis began confiscating the art collections of Jewish families. As German tanks rolled into more European countries, the looting gathered pace, encompassing museums, municipal buildings and religious organisations as well as private citizens. But not all of this activity was directly under the control of the Nazi authorities in Berlin. Individual German officials were lining their pockets, or even doing deals with people fleeing Nazi persecution. Art was becoming an alternative to paper money.

A grand plan
The two greatest collectors among the Nazis were Hitler himself and his flamboyant Luftwaffe chief, Hermann Goering. Between 1940 and 1944, a specially created body based at the Jeu de Paume Museum in Paris confiscated more than 21,000 artworks and other cultural treasures, cataloguing them meticulously. Officials then sent the best pieces (including works by Rembrandt, Titian, Vermeer, Rubens, Van Eyck, Michelangelo and Bruegel) to Linz, Hitler's home town, where a grand Fuhrermuseum was to be established. Other high-profile pieces went to Goering's collection. Lesser works were distributed among German museums. "Decadent", modern art ended up in neutral countries, where it was sold to raise cash.

Allied intervention
As Germany began to lose the military initiative, its art officials began to hide treasures looted from occupied countries. Hitler ordered that his collection should be destroyed if Germany was defeated. Thanks to the British secret services and Austrian anti-Nazis, the collection was saved. As the Allies closed in on Berlin, specially trained U.S. servicemen attached to military units evaluated thousands of artworks uncovered in secret Nazi caches all over Germany.

Restoring ownership
Tens of thousands of artworks were returned to their rightful owners after the war but countless pieces are still unaccounted for. Art dealers in Germany and neutral neighbours operated with little regulation during the war and its aftermath, when items could change hands several times. In recent years, museums outside Germany have had to face up to the unpleasant fact that some of their exhibits may once have been Nazi booty.