Sarant worked on secret military radar at the United States Army Signal Corps laboratories at Fort Monmouth, New Jersey.

Alexandre Feklisov, one of the KGB case officers who handled the Rosenberg spy apparatus described Sarant and Joel Barr as among the most productive members of the group.

A member of the Communist Party of the United States (CPUSA) during the Second World War, Sarant worked at the nuclear physics laboratory of Cornell University.

I must admit that Sarant had the makings of an undercover agent; he was a cautious young man, yet full of resolve, with progressive ideas.

Later, Barr met directly with KGB officers; Sarant did not have direct contact with the KGB in the U.S. One transcript reports Sarant and Barr delivered 17 authentic drawings relating to the AN/APQ-7, an advanced and secret airborne radar system developed jointly by the Massachusetts Institute of Technology and Western Electric for the United States military.

Sarant's next door neighbor was Philip Morrison, a former Manhattan Project scientist and personal friend who joined the Communist Party of the United States in 1939.

Following instructions from the KGB, the Poles hid Sarant and Dayton in Mexico, then engineered an escape that involved crossing the border to Guatemala on foot, taking a freighter to Casa Blanca, and flying to Poland via Spain.

The KGB arranged a dramatic reunion with Barr, who was summoned from Prague, where he had fled shortly after the Rosenberg ring started to unravel.

A Russian émigré working at Harvard, Mark Kuchment, who had read The Rosenberg File linked Barr and Sarant to two prominent Soviet scientists, both native speakers of English.