"Of all of us, he gave the brightest and purest timbre to color," declared Franz Marc after his friend and fellow artist August Macke fell in World War I in 1914. Macke painted his sailboat images at Lake Tegernsee in Bavaria. This painting was among the roughly 1,500 found in the Cornelius Gurlitt collection.

Slender women are a characteristic motif of the influential German expressionist art movement. This model reposes unclothed on a water-surrounded rock.

A difficult, suspicious and depressed man, Kirchner created this wood cutting in 1922. Nazis removed many of his works from German museums and defamed them as "degenerate." Born in the German region of Franconia, Kirchner was buried in Switzerland.

The artist had a reputation for social criticism even as a young man. "I can't get ahead; my paintings can't be sold. I'm either becoming famous or infamous," he said in 1920, not long before finishing this painting.

"My homeland was like a fairytale, my parents' home in the flat countryside, thousands of larks soaring up and down in jubilation, my country of wonder from sea to sea," enthused the North German painter Maler Emil Nolde. Broad expanses and the blurred transitions between sky, earth and water were his motifs.

No motif or animal fascinated Marc more than horse, a metaphor for purity and innocence in the eyes of this expressionist painter. His daring experimentation with color resulted in a group of paintings of blue horses in 1910. This image, also in the Gurlitt collection, was a predecessor.

Modern artworks whose style, artist or subject did not meet with the approval of Adolf Hitler and the National Socialists were labeled "degenerate art." From 1937, the Nazis confiscated such works from German museums. In a traveling exhibition, "degenerate art" was held up for public ridicule. Here we see Reich Propaganda Minister Joseph Goebbels and Hitler at the original exhibition in Munich.

Hitler had an affinity for Romanticism and 19th century painting and preferred peaceful country scenes. His private collection included works by Cranach, Tintoretto and Bordone. Like his role models Ludwig I. of Bavaria and Frederick the Great, Hitler wanted to manage his own art exhibition at retirement, to be shown in the city of Linz on the River Danube in the "Führer Museum."

The National Socialists were not the first to persecute avant-garde artists, but they took it a step further by banning their works from museums. In 1937, the authorities had over 20,000 art works removed from 101 state-owned German museums. Anything that the Nazis didn't consider edifying to the German people was carted off.

Abstract art had no place in Hitler's "national style," as grew clear when the "Great German Art Exhibition" put traditional landscape, historical and nude paintings by artists including Fritz Erler, Hermann Gradl and Franz Xaver Stahl on display in Munich on July 18, 1937. The closer the depicted subject to the actual model was, the more beautiful it was in the eyes of the Führer.

Even those in Hitler's inner circle were highly unsure which artists he approved of. The 1937 "Great German Art Exhibition" and the simultaneous "Degerate Art" exhibition in Munich's Court Garden Arcades brought some clarity. Unwelcome were creative artists of the modern period including Max Beckmann, Otto Dix, Wassily Kandinsky, Paul Klee, Ernst Ludwig Kirchner and Max Pechstein.

In the "Degerate Art" exhibition, 650 confiscated artworks from 32 German museums were on display, the exhibits equated with sketches by mentally handicapped persons and shown together with photos of crippled persons. The intention: to provoke revulsion and aversion among visitors. Over two million visitors saw the exhibition on its tour of various cities.

The "Degenerate Artworks Confiscation Law" of May 31, 1938 retroactively legalized their unremunerated acquisition by the state. The law remained valid in the postwar years, the allies determining that it had simply been a redistribution of state property. Unlike stolen artworks, pieces that the Nazis labled "degenerate" and had removed from museums can be freely traded today.

The confiscated art was taken to storage facilities in Berlin and at Schönhausen Palace. Many works were sold by Hitler's four art merchants: Bernhard A. Böhmer, Karl Buchholz, Hildebrand Gurlitt and Ferdinand Möller. On March 20, 1939 the Berlin fire department burned approximately 5,000 unsold artifacts, calling it an "exercise."

125 works were earmarked for an auction in Switzerland. A commission charged by Hermann Göring and others with liquefying the "degenerate" art products estimated the minimum bidding prices and commissioned the Fischer Gallery in Lucerne to carry out the auction. Taking place on June 30, 1939, it met with eager interest worldwide.

Over 21,000 works of "degenerate art" were confiscated. Estimates on the number subsequently sold differ; sources estimate 6,000 to 10,000. Others were destroyed or disappeared. Hundreds of artworks believed lost turned up in Cornelius Gurlitt's collection — and reignited the discussion.

This drawing by Carl Spitzweg was seized in 1939 from Jewish music publisher Heinri Hinrichsen, who was killed at the Auschwitz death camp in 1942. It was acquired by Nazi art dealer Hildebrand Gurlitt — and later found among the spectacular collection of works hoarded by his son, Cornelius Gurlitt. The work was auctioned by Christie's at the request of Hinrichsen's heirs.

The watercolor by the Jewish painter Max Beckmann entered Gurlitt's collection only in 1945. Held by the allied occupation forces at the Central Collecting Point in Wiesbaden from 1945-1950, it was returned to Hildebrand Gurlitt in 1950. Before working for the Nazi regime, Gurlitt had collected and exhibited modern art, curating Beckmann's last exhibition in 1936 before the artist fled Germany.

This work was owned by lawyer and art collector Fritz Salo Glaser. Artists of Dresden's avant-garde scene were his guests in the 1920s — as was the young Hildebrand Gurlitt. It is not known how Gurlitt came to possess the painting. It was confiscated in 1945 and later returned. Of Jewish heritage, Glaser only narrowly avoided deportation to the Theresienstadt concentration camp in 1945.

This painting by the famous impressionist is not suspected to have been looted. The artist sold it to the Durand Ruel Gallery in 1907. The Jewish art merchant and publisher Paul Cassirer is said to have given it to Marie Gurlitt as a present, and she left it to her son Hildebrand Gurlitt in 1923.

A short handwritten note allowed provenance researchers to identify this work by the French painter as a looted work of art. The picture was seized from the collection of Jewish politician and resistance leader Georges Mandel, who was executed by French fascists near Paris in 1944. German Culture Minister Monika Grütters (right) handed over the work to Mandel's heirs in January 2019.

The activist group Provenance Research Gurlitt identified this painting by French neo-impressionist Paul Signac as stolen Jewish property in October 2018. Gaston Prosper Levy fled Nazi-occupied France in 1940. Occupying soldiers are believed to have looted his art collection shortly before his escape. The painting was returned to Levy's family in 2019.

Hildebrand Gurlitt must have acquired this work by the French sculptor between 1940 and 1945. Previously belonging to the Frenchman Eugene Rudier, it entered circulation in 1919 at an auction by Octave Henri Marie Mirbeau, who is said to have received it as a present from the artist.

This copper engraving by Albrecht Dürer once belonged to the Falkeisen-Huber Gallery in Basel. It is not known how it got there or how long it was there however. In 2012 the engraving turned up in Cornelius Gurlitt's collection. "Old masters" like Dürer were very important to the National Socialists' view of art and were often exploited for propaganda.

The provenance of this drawing is completely unknown. It is certain, however, that Hitler considered Norwegian artist Edvard Munch's work "degenerate art." Some 82 pieces by Munch were confiscated in German museums in 1937.

Hitler venerated 18th-century French painting. He secured exceptional paintings for his own collection by targeting the collection of the Rothschild Family after the annexation of Austria. Hildebrand Gurlitt supplemented them with drawings by renowned French painters. He acquired this work by Boucher from a Parisian art merchant in 1942.

Cornelius Gurlitt hoarded the sculpture along with many other artworks for decades in his Munich apartment. Before his death in 2014, he consented to have his stocks researched and — should they include articles of stolen art — have them returned to their rightful owners in accordance with the Washington Principles on Nazi-looted art.