When Carla Schulz-Hoffmann, the head of 20th century art in the Bavarian State Painting Collections attended a landmark conference on Holocaust-era assets in Washington in 1998, she was the only person from a German museum there. The conference featured leading historians from 44 nations setting out the magnitude of the art theft under the Third Reich.

The accounts of massive pillaging and the subsequent struggle for restitution shocked Schulz-Hoffmann. Lynn Nicholas, the author of The Rape of Europe, described Nazi art looting as 'the greatest displacement of works of art in history'.

And Jonathan Petropoulos, a historian, called for a collaborative effort to reconstruct the details of thefts and 'transfers of ownership' as Nazi forces plundered their way across Europe.

The conference agreed that special resources should be made available to help identify and publicise artworks that had not been restored to their former owners. The heads of Munich's national galleries took this to heart and asked the art historian Ilse von zur Muehlen to research the provenance of the entire post-1933 part of their collection, of which 800-900 objects were 'owned' by Nazi functionaries or the Nazi party itself.

Eventually, von zur Muehlen's task was restricted to the objects that had belonged to Adolf Hitler's henchman, Reichsmarschall Hermann Goering. She has set out the results of her complicated forensic activities in a new book that was published this summer.

With 30,000 works of art, the Bavarian state collection is the world's biggest, comprising 9,200 objects acquired after 1933 and housed in three Pinakotheks in Munich, the state capital. 'It has taken so extraordinarily long to establish the ownership of works in our collections, which is awful,' Schulz-Hoffmann says. 'Everything was started far too late for many heirs of those who suffered Nazi persecution.'

But things have changed and Schulz-Hoffmann says it is amazing how much research is now being done. The Bavarian state collection was not the only German museum to employ dedicated staff to research their holdings (albeit employed on limited contracts) but it was the first to publish a provenance report.

Even narrowed down to 126 artworks, the first systematic probe by a German museum into its Nazi-era assets was going to be daunting. Tracing provenance led von zur Muehlen to the federal government archives in Coblenz. There she discovered a huge number of documents, which she copied and transported to Munich to complete the work of comparing inventories.

This involved decyphering a series of different numbers, chalked or stuck on back panels, evaluating inventories and delving into the identities of many individual buyers and dealers. While doing this she had to be aware that Goering's accomplices tried to give the transactions a legal veneer.

The Goering cache in Munich comprised only a fragment of the vast number of works accumulated by the Nazi Reichsmarschall. By 1937 Goering was in charge of aviation, hunting, forestry, raw materials and currency as well as the exchequer. These posts paid him about 150-180 million Reichsmark: over £3m a year in today's money. Gifts from industrialists further swelled Goering's coffers.

Goering used every opportunity to satisfy his greed for artworks. One of the key organisations for systematic Nazi art theft was the Einsatzstab Reichsleiter Rosenberg (ERR). The unit, formed to go through libraries and archives to ferret out 'anti-German' material, was also used to seize valuable cultural goods from Jewish owners.

As Nazi forces occupied more and more countries, Goering used the ERR to transfer art to his private collection. He made 20 trips to Paris to take his pick of no less than 594 works from the depot in the Jeu de Paume, which housed 22,000 looted art objects.

After the defeat of the Luftwaffe in the air battles over England and the surrender at Stalingrad, Hitler's confidence in Goering waned, and the corpulent art lover fell back into his morphine addiction. Dressed in fantasy uniforms he retired to his country estate Carinhall, and surrounded himself with canvases and statues.

On 29 April 1945 Hitler disowned Goering and he was arrested by the SS and taken to Mauterndorf castle in Austria. American forces arrested him on 8 May. At the Nuremberg trials he was accused of 'plundering public and private property' and systematic art theft. He was sentenced to death by hanging but avoided this fate by committing suicide.

Goering's art collection had reached astonishing proportions by the time of his death. It included 1,375 paintings, 250 sculptures, 108 tapestries, 200 items of antique furniture, 60 Persian and French carpets, 75 stained glass windows and other works of art. Sifting out the story of these items has been made doubly difficult because of the chaos that ensued in the last months of the war.

In July 1944, Goering shipped his booty from occupied France to Carinhall on a special train. In January 1945 he decided to move his entire collection south to Veldenstein castle near Nuremberg and to Berchtesgaden in the Alps. An inventory was compiled but it has never resurfaced.

One train left Carinhall on 17 February 1945 and arrived at Veldenstein and a second made it to Berchtesgaden. But a third containing large canvases was delayed by bomb attacks. At Veldenstein it was discovered that the castle's corridors were too narrow to allow passage, so the paintings were loaded back on to the trains.

All four trains finally reached Berchtesgaden by 12 April, but then remained unloaded for two weeks, shuttled into various tunnels to escape the bombing. Frantic attempts to stow away the precious trainloads were interrupted when the Allies marched in on 4 May. But before they arrived on the scene, French troops had found the trains and looted them, firing machine-gun volleys into the wagons.

Bullet holes and damp and poor conditions in the tunnels and bunkers affected many treasures. Using whatever documents were to hand, the US forces numbered the pictures, before shipping them to the newly opened Central Collecting Point in Munich at the end of World War Two.

Set up by a team of US officers who were assisted by local German experts and international staff, the unit made sure that a large proportion of the artworks swiftly found their way to their original owners.

Craig Hugh Smyth, a young naval lieutenant put in charge of the Monuments, Fine Arts and Archives Section of the military government of Bavaria, organised a document centre to help determine the ownership of the artworks. On 21 August 1945 the first artwork to go back was the Ghent altarpiece from Belgium.

In 1952 all unclaimed works were supposed to be transferred from the jurisdiction of the Bavarian government to the new federal German Republic, which was under formation. But legal arguments went on for a decade.

Finally the Bavarian and the federal governments agreed to divide the items between them. The new acquisitions report simply describes them as 'transferred from [federal] state ownership in 1961', thus avoiding any mention of Goering's ownership.

The then director of the Barvarian state collections, Kurt Martin, was anxious about restitution demands as well as the activities of the extreme right. There were also fears that the remainder of the Nazi collections might be shipped en masse to the US for auction.

The Goering provenance report is a major effort to bury the ghosts of the past and provide possible claimants with as much information as possible. It includes not only those items currently in the Bavarian state collections, but also those auctioned in 1961.

In Germany, the response to the report has been mixed. Some say that a line should now be drawn under the whole Nazi era. But Der Spiegel magazine claimed there was complacency now the report had been published.

Some feel there is still a sluggish attitude towards unravelling the ugly truths that may lie behind a seemingly innocent purchase during the Nazi years.

So far there have been no claims for restitution, but Schulz-Hoffmann believes that the Goering report will encourage people to come forward to fill in remaining gaps. Will the research go on? She regrets that there is no more money to employ special staff, but says that all the curators are obliged to check provenance.

Out of the 1,000 objects from the Nazi epoch, she believes 110 'definitely are difficult', and require special investigation. Other people, including von zur Muehlen, believe it is impossible to determine how many are suspect until all ownership gaps between 1933 to 1945 are filled in.

Corinna Lotz is an art historian and critic. Her father, Wolfgang Lotz, worked at the Munich Collecting Point with Craig Hugh Smyth in 1946

The Art Collection of Hermann Goering, a Provenance Report by Ilse von zur Muehlen, is published by the Bavarian State Painting Collections. It is available from
www.cedon.de
The paper chase

While researching the provenance of Pyramus and Thisbe (pictured), a painting from the school of Lucas Cranach the Elder dated 1518-20, the art historian Ilse von zur Muehlen has closed some of the gaps about the painting's ownership that were left after a postwar investigation.

The painting once belonged to the artist Wilhelm Truebner, and was sold in Berlin at auction after his death in 1917. In 1931 it entered the collection of Stephan von Auspitz, the director of the Kreditanstalt Bank in Vienna. Von Auspitz, who was of Jewish origin, ran into financial difficulties with the Austrian government.

After the bank failed, his collection was purchased by a Dutch businessman, George van Beuningen of Rotterdam, who in turn sold part of it to Kurt Bachstitz, a native Austrian. A contemporary magazine shows the painting in the Bachstitz Gallery in Den Haag.

In August 1937 Goering bought the Pyramus and Thisbe painting through his dealer, Walter Andreas Hofer, for 10,000fl. But what happened between 1931 and 1937, during which time the Nazis seized power in Germany and annexed Austria?

Pyramus and Thisbe may have left Austria before the export ban set up under Nazi rule in 1938 and travelled to the Dutch dealer in The Hague, or it may have been sold directly to Bachstitz in Vienna.

In either case, a shadow is cast over the sale as Bachstitz was Jewish, and also Hofer's brother-in-law. According to the US Goering Report, Hofer refused to ask Goering to protect Bachstitz from anti-Semitic laws, thus placing Bachstitz under great pressure to sell.