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If lined up alongside the motley crew of bohemian artists living and working in Paris at the turn of the 20th century, Henri Matisse would seem like a tame, middle-aged painter. Bespectacled, a bourgeois father of three, and with a background practicing law, Matisse was hardly the usual suspect for a rule-breaker.

Radicals can sometimes sprout from unexpected sources, though. From underneath his conventional exterior, Matisse painted fiercely colorful canvases that challenged audiences who had not yet come to terms with the expressive paintings of Vincent van Gogh and other Post-Impressionists, painted a little over a decade before.

Matisse was the ringleader of one of the earliest avant-garde art movements in 20th-century France: Fauvism. This short-lived style, whose public heyday was between 1905 and 1908, translated nature into vibrant colors applied straight from the paint tube and smeared onto the canvas with forceful brushstrokes. It opened the doors for radical departures from accepted practice: mountains tinged with purple, sun-drenched fields saturated with fiery reds, and shadows on human faces that were pure vermillion and green.

“Even when [an artist] consciously departs from nature,” Matisse wrote in 1908 of his choice to interpret the world into a rainbowlike palette, “he must do it with the conviction that it is only the better to interpret her.”

Matisse certainly had conviction and would continue to use high-octane colors for the rest of his illustrious career. When the critics first saw these works in 1905, though, they were less convinced of the virtue of pure, unmixed hues.

A Donatello among wild beasts

During the summer of 1905, Matisse and fellow painter André Derain worked together in the southern French fishing town of Collioure. Liberated by their distance from Paris, the pair filled their canvases with shockingly prismatic landscapes. A few months later, they exhibited a selection of these recent works at the Salon d’Automne, astonishing audiences with their brutally vibrant interpretations of quaint, countryside views.

Matisse’s and Derain’s paintings filled Room VII of the Salon, where two traditional sculptures by Albert Marque were also on view. “The candor of these Marque busts is surprising,” wrote prominent art critic Louis Vauxcelles in his exhibition review printed in Parisian literary journal Gil Blas, “in the midst of the orgy of pure color: Donatello among the wild beasts.”

Vauxcelles considered the bright paintings surrounding Marque’s more traditional sculptures to be savage by comparison, so he used the French word for wild beasts—fauves—to describe them. But he did balance his verbal assault with some praise for Matisse’s brave experimentation. “Matisse is one of the most robustly gifted of today’s painters. He could have obtained easy bravos: He prefers to drive himself to undertake passionate experiments.”

Other critics were less inclined to see the plus side of all this orgiastic color, barbing their reviews with zingers (that were likely fun to write). Art critic Camille Mauclair described the works exhibited at the 1905 Salon d’Automne as “a pot of colors flung in the face of the public.” Another journalist characterized the works as “barbarous and naïve games of a child playing with a box of colors.” Derain and fellow painter Maurice de Vlaminck were accused of using their colors like sticks of dynamite.

Charles Morice, a Parisian writer, somewhat vaguely wrote in the Mercure de France journal that “we are at the beginning of ‘something else.’”

That ‘something else’ was ultimately defined by Vauxcelles; as of 1906, the colorful style championed largely by Matisse was known as Fauvism.

Even after the movement was typified by ferocity, it had its public defenders. “We are not here in the presence of an extravagant or extremist undertaking,” concluded poet and art critic Guillaume Apollinaire in a 1907 article about Matisse. “Matisse’s art is eminently reasonable.”

Who were the wild beasts?

Unlike other movements of the early 20th century, the Fauves were a loosely organized group of painters led by their oldest member: Matisse. They shared bold use of color and wildly aggressive brushstrokes but were otherwise vaguely defined and mostly held together by friendship. The Fauves included Maurice de Vlaminck, Kees van Dongen, Charles Camoin, Henri-Charles Manguin, Othon Friesz, Alice Bailly, Jean Puy, Louis Valtat, Georges Braque, and Raoul Dufy.

For many of these artists, Fauvism was a transitional stage between styles. Braque, for example, abandoned color altogether a few years later when he pioneered a highly monochromatic Cubism with Pablo Picasso. (The Cubist movement, coincidentally, also got its name from a slanderous review penned by Louis Vauxcelles.) By 1907, Derain and Matisse went off in different creative directions and Fauvism fizzled.

Matisse, though, stayed his colorful course, even if he wasn’t a fan of his beastly nickname. In an interview for The New York Times Magazine in 1912, Matisse pleaded with journalist Clara T. MacChesney: “Oh, do tell the American people that I am a normal man.”