Adventures of a masterpiece: a remarkable episode in art history

A young woman dozes on a couch wearing only white silk stockings and a contented expression. The curtains behind her have been pulled aside, revealing a window and the light fading in an overcast sky. An afternoon of passion is approaching its close.

For six decades, this erotic masterpiece by the French "realist" Gustave Courbet – a bully and a braggart, one of the great painters of the female nude and an important influence on the Impressionist movement – was missing, believed stolen by either the Nazis or the Red Army.

The canvas, Femme Nue Couchée, has now resurfaced. Next month the painting will make its first public appearance since 1940 as part of the largest Courbet exhibition for 30 years, at the Grand Palais in Paris.

The strange saga of what happened to the painting, and how it came to be recovered, is only just starting to emerge. Courbet's missing erotic masterpiece is believed to have spent most of the past 60 years on the wall of the home of a country doctor in Slovakia. How it came to be there, and how it came to be returned to the heirs of its wealthy Hungarian-Jewish owner, is a tangled and fascinating story.

Some details remain lost in the mist of the final, brutal months of the Second World War. Other details remain confidential as part of the agreement which returned the painting to its rightful owners for a "reward" of ¿500,000 (£350,000). (Courbet paintings can fetch up to £2.5m at auction.)

In the early months of 1945, as the Red Army advanced across eastern Europe, a group of Russian soldiers banged on the door of a doctor in a village near Bratislava. One of their comrades was wounded. They had no money to reward the doctor for treating their friend. They did, however, have a rolled-up painting.

The doctor agreed to help the soldiers. The Russians – who could presumably have forced the doctor to work at gunpoint – gave him the painting and left. The doctor put the painting – a beautiful portrait of a reclining nude – inside a cheap glass-covered frame and placed it on a wall of his house.

If this story can be believed, the unknown, wounded Russian soldier had one of the most expensive medical consultations in history.

Charles Goldstein, attorney for the Commission for Art Recovery in New York, which negotiated the painting's return, said: "We have an affidavit from members of the doctor's family swearing that this was the story that he always told of how he came to obtain the painting. There is no reason to disbelieve them." The saga of the missing Courbet nude is part of a complex and shameful story of systematic art theft during the Second World War. The shameful part did not end with the war in 1945. Thousands of art treasures are still missing; others, even more shamefully, are not missing but displayed on the walls of art galleries in Moscow, Budapest and elsewhere.

If the patrol of Russian soldiers had not "paid" the Slovak doctor with the Courbet nude, it would probably have ended up, like many other looted, Jewish-owned art works, on the walls of the Pushkin gallery in Moscow. Some Jewish-owned art works were stolen twice during the Second World War, first by the Nazis and then by the Soviets. Others were pillaged directly by the Red Army. Moscow – both communist Moscow and post-communist Moscow – has consistently and adamantly refused to return them.

The Femme Nue Couchée belonged to Baron Ferenc Hatvany, head of a Hungarian-Jewish banking and sugar-making family. Hatvany, an amateur painter himself, was more interested in art than sugar or money. From 1908, he assembled one of the largest and most admired art collections in Europe, running to more than 2,500 works.

He was especially interested in French 19th-century artists – Ingres, Manet, Renoir and, above all, Gustave Courbet. In 1913, Baron Hatvany bought two Courbet canvases.

One, purchased in a gallery in Paris, was the most notorious of all Courbet's works, a startling and beautiful study of a woman's splayed thighs and genitals, called L'Origine du Monde. The other, purchased in Berlin, was Femme Nue Couchée, part of a series of nudes painted by Courbet in the 1860s which were considered controversial – even scandalous – in their day but helped to shift 19th-century art away from the formal and academic to the actual and the human.

Courbet (1819-1877) is a complicated figure, whose work has, until recently, fallen under the shadow of the Impressionists who came after him. He was a notoriously rambunctious and boastful man: a kind of artistic Jose Mourinho.

"I have astounded the entire world," he once said. "I triumph not only over the moderns but over the masters as well."

He was one of the first painters to experiment with photography. He circulated photographs of his work and even press releases about his activities.

Ultimately, he fell foul of his own left-leaning political activism. He advocated the destruction of the column in the Place Vendôme in Paris during the Commune of 1870-71. When the mob took him at his word, the French government sent him the bill for a new column and he fled to Switzerland.

The Grand Palais exhibition, from 13 October to 28 January, with 120 paintings and 60 photographs, is part of a movement to rediscover his work.

At the beginning of the Second World War, both of the Courbet nudes bought in 1913 – and many other paintings – were hung in Baron Hatvany's large private house near the royal palace in Budapest.

The Femme Nue Couchée was in one of the large reception rooms. L'Origine du Monde was banished to the baron's personal bathroom.

In 1942, the pro-Nazi government in Hungary moved to expropriate all Hungarian Jews. Hatvany managed to place his most valuable paintings – including the two Courbets – into private bank vaults, under the name of non-Jewish, Hungarian friends.

He and his family fled the country before the Germans took over in March 1944. More than 500,000 other Hungarian Jews, less prudent, less well-off, less well-connected, were unable to escape. They were deported to Auschwitz and died in the gas chambers.

After the war, Hatvany returned to Budapest and found that his bank vaults had beenpillaged. It was not clear whether his possessions – and those of other wealthy Hungarian Jews – had been stolen by the Nazis or by the Red Army, which captured Budapest in January 1945, or by the Hungarian authorities. A Russian military commission was known to have toured the bank vaults and carted off anything they believed was valuable.

In 1946, in circumstances still unclear, Hatvany managed to buy back his notorious Courbet nude, L'Origine du Monde, from the Soviet Union. Very few other stolen paintings have ever been returned by the Soviet or Russian authorities. Perhaps the subject matter of L'Origine du Monde was too stark for the communists to cope with.

This painting was later acquired by the French philosopher-psychoanalyst, Jacques Lacan. After his death, it passed to the French state in partial settlement of death duties. It can usually be seen in the Musée d'Orsay but will be among the Courbet paintings in the Grand Palais exhibition – reunited with its sister nude from the Hatvany collection for the first time in 65 years.

Baron Hatvany spent the remainder of his life until 1958 trying to trace his art collection. Less than five per cent of it was ever recovered. "Most of the pieces have simply disappeared," said Mr Goldstein of the Commission for Art Recovery, set up to track down stolen Jewish-owned artworks. "Some, we know exactly where they are. They are on the walls of the Pushkin museum in Moscow and the arts museum in Budapest. But that doesn't mean we can get them back."

Nothing was heard of the Femme Nue Couchée for 55 years. In 2000, a Slovakian arts and antique dealer, operating through an American go-between in Prague, contacted Christie's auction house.

"Whether the family realised just how valuable the painting was is unclear," Mr Goldstein said. "The old man might not have known what he had for many years but, at some point, I suspect, the family did know."

Christie's identified the painting but also identified it as stolen property and refused to deal with it. Instead, it put the Slovak dealer and the American intermediary in touch with the Commission for Art Recovery.

There followed five years of shadow-boxing. Mr Goldstein, who was at the centre of the negotiations, said: "As long as the American intermediary was involved, we got nowhere. The contacts broke off. We placed an advertisement in every publication in Slovakia offering a reward for the painting. The antique dealer and family got back in touch. Eventually we agreed a reward – not a purchase price – of ¿500,000."

"Even then we had months of negotiations ahead of us to obtain an expert permit from the Slovak government. In eastern Europe, nothing is easy."

The painting returned to Baron Hatvany's heirs two years ago amid considerable secrecy. The shroud of confidentiality has only been lifted – partially – with the agreement of the painting's owners to lend it to the exhibition in Paris.

This will be the first public viewing of the painting – other than by the Slovak doctor's presumably goggle-eyed patients and friends – since it appeared at the Budapest fine arts museum in the spring of 1940. Much remains unclear – or unsaid. How did the painting come to fall into the hands of a group of ordinary Red Army soldiers?

The booty from the bank vaults in Budapest is believed to have been loaded on to a train, bound for Moscow. Was the train pillaged, or re-pillaged, by Russian troops?

"We can tell from the condition of the painting that it was rolled up at one time," Mr Goldstein said. "It has also been damaged, not seriously, in a way that suggests it was exposed for a long time under glass. Otherwise, it is in remarkably good condition."

The great irony, for Mr Goldstein, is that the painting would never have been recovered by the Hatvany family if it had not been "acquired" by the soldiers and given to the Slovak doctor in return for medical care.

"Dealing with private individuals can be a nightmare but it is always much easier than dealing with governments," he said. "If this painting had got as far as Moscow, it would still be there to this day."