In 1936, Martha Graham received a letter from the Third Reich, inviting her to participate in the Summer Olympics in Berlin. In response, the dancer and choreographer scribbled on the page:

“Cannot accept invitation – Letter follows – M.g.”

Graham’s subsequent letter reads: “So many artists whom I respect and admire have been persecuted . . . I should consider it impossible to identify myself, by accepting the invitation, with the regime that has made such things possible.”

A small protest in a conflict so large, the document is part of the exhibition “Politics and the Dancing Body” at the Library of Congress that casts the history of modern American dance in a new light — as an art form that explored, protested, and promoted the tumultuous U.S. landscape between World War I and the Cold War. Along with such archival material, the show includes photographs of dancers frozen in action, where the human body is a document of its time.

In the era of the Great Depression, for instance, the reality of physical labor became a muse. Images capturing Jane Dudley’s 1938 “Harmonica Breakdown” show the dancer’s anguished shuffling and contorting as she references the life of African American sharecroppers, in both struggle and rebellion. (A video nearby offers a contemporary performance of the work.)

The subject of labor also informed performance groups captivated by the Communist Party. The Marxist-leaning New Dance Group (co-founded by Dudley) is depicted in “Improvisation” from 1932, where a collective of dancers wearing stern expressions groups together with bodies tensed and fists tightened to show unified strength.

For their link to communism, many dancers were later targeted by the House Un-American Activities Committee. As shown in a facsimile of a FBI report from 1944, Dudley was among the choreographers put under surveillance, and her husband, documentary filmmaker Leo Hurwitz, was blacklisted.

Dancers also responded to America’s internal struggle with racism, as seen in Charles Weidman’s “Lynchtown” from 1936. In the image by noted dance photographer Barbara Morgan, a cluster of figures leap forward in synchronic movement to simulate the forward drive of a lynch mob and are lit dramatically from the rear as they dive into darkness.

Also during the Depression, the federal government was working to support the dance community, as President Franklin D. Roosevelt implemented the Federal Theatre Project as part of the Works Progress Administration from 1935 to 1939. By the advent of the Cold War, dancers were being sent abroad and used as cultural ambassadors around the world to promote American values.

In 1941, the government, through Nelson Rockefeller as the coordinator of inter-American affairs, sent dancers around South America to counteract anti-American sentiment. One participant was Lew Christensen, whose “Filling Station” told the story of ordinary Americans such as “Mac,” a gas station attendant dressed in a stylized, plastic version of the classic uniform.

The State Department also sent Graham’s company on a tour in 1955 through Asia, including Burma, India, Pakistan, Japan and the Philippines. A poster from Graham’s performance in Japan depicts an odd version of the dancer as part movie star and part body-builder, showing her as, above all, an American export and commodity.

Such promotion of American culture was not unique to dance. In 1946, for instance, the State Department purchased 79 paintings by American artists — among them Romare Bearden, Ben Shahn, and Georgia O’Keeffe — and toured the collection from Latin America to Prague.

Sending arts on tour allowed the United States to control its image abroad. In 1962, when the Soviet Union was condemning America for its racial injustice, the State Department sent African American dancers Alvin Ailey and Carmen de Lavallade on a tour to Australia and Asia. Then eight years later, in the midst of the Vietnam War, Alvin Ailey’s company became the first American modern dance group to visit the Soviet Union — as shown in a snapshot of the dancers as tourists in Leningrad.

Though these photographs are now weathered, part of the archival collection of the Library of Congress, they attest to a tradition that still exists today, even in a generation in which the most obvious ambassadors of American culture are movies, fast-food restaurants, and retail chains.

In 2010, the State Department launched the cultural diplomacy program DanceMotion USA, which will send four groups abroad. First up is the hip-hop company Rennie Harris Puremovement, which will tour Egypt, Israel, and the Palestinian territories next month. The $1.7 million project represents a small portion of the Bureau for Educational and Cultural Affairs’ nearly $500 million budget. Yet it speaks to the continued interest in using dancers as ambassadors, in the promulgation of the American way.

O’Steen is a freelance writer.

Politics and the Dancing Body

Through July 28. Open 8:30 a.m. to 4:30 p.m. Monday through Saturday.

Performing Arts Reading Room, James Madison Building, Library of Congress,

101 Independence Ave. SE.