The Hirshhorn Museum and Sculpture Garden has made its most important purchase to date: one of eight existing casts of "Action in Chains," an enormously imposing, 7-foot-high bronze by the French sculptor Aristide Maillol (1861-1944).

The statue - of a robust standing nude, her wrists bound behind her back - cost nearly $400,000. Half of the money came from a Smithsonian Institution fund set aside last year for major museum acquisitions; matching funds were donated by the museum's board of trustees.

Most of Maillol's nudes seem both classical and primitive: static simplified, serene. Very few are as vigorous as this one. Abram Lerner, the museum's director, says her forceful pose "echoes a tradition in sculpture that has surfaced throughout history, from the 'Winged Victory' of Samothrace to Rodin's 'Walking Man.'"

"Action in Chains" is an allegorical figure. The statue was commissioned in 1905 by Anatole France, Georges Clemenceau, and other France, Georges Clemenceau, and other Frenchmen of the left as a monument to Louis-Auguste Blaqui, a 19th-century politician and theoretician who so threatened the regime that in his long career he spent nearly 30 years in jail. His nickname was "the prisoner" - hence the statue's bonds.

The first cast of the sculpture was installed in 1906 in Blanqui's home-town in Provence. In 1929, the artist had a second cast made for the Albertina Museum in Vienna. In accordance with his wishes, six additional casts were made after his death. Of those, the Hirshhorn's is the last. Purchased through New York's Perls Galley, it was once owned by Dina Vierny, one of Maillol's models and later the executor of his estate.

Maillol began his career by providing illustrations for a small provincial magazine. After copying the paintings in a neighborhood museum, he decided to become a painter and moved north to Paris where he studied with Gerome at the Ecole des Beaux Arts.

In 1890, encouraged by his friend Paul Gauguin, he left school to set out on his own. Six years later he began to carve in wood. "Action in Chains," his first big commission, gave him great difficulties. It is said that in despair, enraged by his failure to find a pose that pleased him, he once smashed the still-unfinished statue and offered the commission to his friend Henri Matisse.

Rarely in the past have the national art museums competed with each other for major acquisitions, but that situation now seems to be changing. Though the National Gallery surely could have used a bronze Maillol of such a scale, the Hirshhorn acquired it. There is an additional irony in the fact that the National Gallery, now augmenting its 20th-century collection, recently paid nearly $1 million for six paintings by Arshile Gorky. Its sister museum across the Mall already owns 21.

"Action in Chains" goes on view today on the third floor of the Hirsh-morrow on the third floor of the Hirshhorn.Eventually, it will be permanently installed outside in the museum's sculpture garden. CAPTION: Picture, no caption