SECURITY LEVEL: COSMIC.
TO: Mr. J. Edgar Hoover, Director, Federal Bureau of Investigation.
FROM: Mr. Clyde Tolson.
DATE: 29 March 1951.
RE: Possible Further Security Breach, Manhattan Project.
Saypol telephoned. The Rosenbergs have been convicted. He anticipates that Judge Kaufman will impose a harsh sentence. Therefore, the Rosenbergs undoubtedly will inform on their KGB contacts. They would have to be heartless fanatics not to do so. Testifying will save their lives and not leave their sons as orphans.
It is vitally important, that they provide full and forthcoming information. Recent information suggests that the security breach at Los Alamos may be more complicated than the Bureau had first understood. This opens new lines of investigation that must be pursued.
At some undetermined point, Julius Rosenberg and/or Harry Gold may have supplied information on atomic weapon design to others in addition to the Russians. The NYPD “Red Squad” has—informally–reported that both men met several times with “Walter Glassman.” The FBI assesses that this person is identical with “Vladek Spiegelman.”
Bureau legal attache, Mexico City, reports that one “Gualtiero Vidrio” [translates as “Walter Glass”] entered Mexico through port of Veracruz traveling on a European Union passport. The men may be identical.
Vidrio/Glassman/Spiegelman is NOT known to be a Russian operative.
Who does he represent?
How, when, and for what purpose did he arrive in the United States?
 Irving Saypol, born 1905; BA, Saint Lawrence University, JD, Brooklyn Law School; United States Attorney for the Southern District of New York.
 Julius and Ethel Rosenberg. Espionage agents of the Soviet Union.
 Irving Kaufman, born 1910; JD, Fordham University School of Law.
 FBI Special Agent James Joseph Kelly conferred with NYPD Detective John Gerald Kelly (the men are brothers) at “The Slaughtered Lamb,” a bar in Brooklyn on Saturday, 24 March 1951.
 Born 1906, Czestochowa, Russian Empire. Primary school education only. Textile dealer. Spiegelman was relocated from Poland to Madagascar, 1941. Arrived in the United States on date and by means uncertain. Agent evaluations of Spiegelman/Glassman range from “modest/unassuming/deferential” to “ruthless and calculating.”
 Passport information states that Vidrio was born in 1906, Czestochowa, Russian Empire. Lately resident of Berlin, German Reich.