Charles J. Mendelsohn

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Charles Jastrow Mendelsohn (8 December 1880 - 27 September 1939) was an American cryptographer and classicist.[1] He was the only child of Rabbi Samuel Mendelsohn and Esther Jastrow.[1][2][3]

He was born in Wilmington, North Carolina.[1]


He graduated from the Episcopal Academy, Philadelphia in 1896.[1] He was a Harrison Scholar at the University of Pennsylvania, which he graduated with a Bachelor of Arts in 1900 and a PhD in 1904.[1] He was a member of Phi Beta Kappa.[1] He joined the faculty of College of the City of New York as a tutor in Greek in 1905, becoming an instructor in 1907.[1] He was a professor of ancient languages in 1917.[3]

Military Service[edit]

During World War I he served in the censorship department of the Post Office Department in 1917, dealing with foreign language, postal and newspaper censorship.[1][3] His work came to the attention of Herbert Yardley and he was recruited into Military Intelligence, section 8 (MI-8).[3] From 1918-19 he was a captain in the Military Intelligence Division of the War Department General Staff.[1]

He led a team dealing with German diplomatic correspondence, breaking at least six diplomatic ciphers.[3] Two messages dealt with German attempts to get support from Mexico.[3]

He received an honorable discharge.[3]

Return to civilian life[edit]

He returned to City College in 1920 as a professor of history.[1][3] He remained interested in cryptography, writing papers and became interested in the history of the topic, collecting many books on it.[1]

He remained in contact with Herbert Yardley and did part time cryptographic work for the Black Chamber.[3] Together they published the Universal Trade Code, a commercial code.[3] He wrote several works for the Black Chamber, including The Zimmermann Telegram of January 16, 1917 and its Cryptographic Background and Studies in German Diplomatic Codes Employed During the World War.[3]


In 1939, he was recalled to active duty as a result of World War II, but while preparing he contracted meningitis and died of it.[1][3]

His library, which had been called "probably the most important cryptographic library in America, if not in the world" was bequeathed to the University of Pennsylvania.[1]

He had never married and was survived by his mother.[1] He was buried in the Hebrew Cemetery at Oakdale Cemetery, Wilmington, North Carolina.[1]


  • Studies in the Word-Play in Plautus[1]
  • The Zimmermann Telegram of January 16, 1917 and its Cryptographic Background[3]
  • Studies in German Diplomatic Codes Employed During the World War[3]


  1. ^ a b c d e f g h i j k l m n o p Dictionary of North Carolina Biography. University of North Carolina Press. Retrieved 16 March 2018.
  2. ^ Jewish Encyclopedia. Funk & Wagnalls.
  3. ^ a b c d e f g h i j k l m n Bandel, Jessica (9 November 2017). "Wilmingtonian Decodes German War Correspondence". North Carolina Department of Natural and Cultural Resources. Retrieved 16 March 2018.