Almost as intriguing as the cache is the serpentine story of the documents’ rescue and rediscovery, much of which had been known before but which has been updated with the new find.

When the Nazis occupied Lithuania from 1941 to 1944, they were determined to incinerate or grind up the country’s Jewish collections, particularly those at YIVO, which from 1925 to 1940 in Vilna was the world’s foremost library of Jewish life in Eastern Europe. With characteristic incongruity, though, they decided to save a third of the YIVO collection for a research center near Frankfurt that would study “the Jewish question” even if they planned to make sure the Jews would be extinct. (In Lithuania alone, 90 percent of the prewar Jewish population of 160,000 was murdered.)

They needed Yiddish speakers to analyze and select the materials, and deployed 40 ghetto residents like Sutzkever and another raffish poet, Shmerke Kaczerginski, as slave laborers. Risking death by a firing squad, this “paper brigade” rescued thousands of books and documents.

When the Germans were pushed out of Lithuania by the Soviets, survivors like Sutzkever spirited some hidden treasures to New York. (The Soviets frowned on anything evocative of ethnic or religious loyalties.) Meanwhile, a gentile librarian, Antanas Ulpis, who was assembling the remnants of the national library in a former church, St. George’s, stashed stacks of Jewish materials in basement rooms to hide them from Stalin’s enforcers. He is, as a result, regarded by YIVO as a kind of Oskar Schindler of document rescue.