Simulated Paper-and-Pencil Codebreaking of a Ciphered Letter of Mary, Queen of Scots

I uploaded a new article "Simulated Paper-and-Pencil Codebreaking of a Ciphered Letter of Mary, Queen of Scots", which demonstrates how paper-and-pencil codebreakers could have broken a cipher used in a letter from Mary, Queen of Scots, to James Beaton, Archbishop of Glasgow (1586).
Remember that I did not break this cipher myself. The article only "simulates" how it could have been achieved by codebreakers such as Thomas Phelippes without using computer tools.

An English Polyalphabetic Cipher from the Seventeenth Century

I uploaded a short new article "An English Polyalphabetic Cipher from the Seventeenth Century". No specimens enciphered with this are known to me.

"Operational History of Japanese Naval Communications"

After WWII, the Japanese Government conducted war records investigation under instructions from the GHQ (the General Headquarters of the Supreme Commander for the Allied Powers). After the War Ministry and the General Staff were dissolved, the work was conducted under the supervision of the Demobilization Bureau. Records were compiled by former officers who had been on duty during the war. An English version was distributed as
Operational History of Naval Communications: December 1941-August 1945. Japanese Monograph No.118 (Department of the Army: Office of the Chief of Military History, 1953) (pdf)
I learned of this by a citation in Chapter 17 of David Kahn, The Codebreakers. When I bought its paper reprint twenty years ago, I did not have access to the Japanese original. Now, the original (海軍作戦通信使), prepared by the Second Demobilization Bureau and dated March 1949, can be found at JACAR (Ref: C19010076600).
An edition by the Service School of the Safety Security Force (警備隊術科学校), dated 1953, is also available in pdf on Akio Tsutsumi's website ().

(Nonsecret-)Coded Military Telegram of Imperial Japanese Army (1936)

I found a coded telegram of the Imperial Japanese Army from September 1936 in JACAR C01004245300. The code is a telegraphic code not intended for secrecy.
I added its transcription in an article in Japanese. (The abridged version in English, "Japanese Telegraph Codes", has not been updated recently. I hope machine translation will help reading the Japanese article.)

A Cipher Letter to Henry VII from John Stile

John Stile was among the first to use cipher in English diplomatic correspondence. In "Earliest English Diplomatic Ciphers", I said he wrote many cipher letters at the end of Henry VII's reign, but my source was a secondary source. The other day, I reconstructed Stile's cipher from manuscript of his letters to Henry VIII. Now, I confirmed his cipher letter dated 26 April 1509 was addressed to Henry VII (the news of the death of Henry VII had not yet reached Spain).
Although the letter is known in calendared text, the printed text is much shorter than the plaintext deciphered from the cipher letter.

Ciphers of John Stile and Thomas Spinelly (1510s)

I added my reconstruction of ciphers of John Stile and Thomas Spinelly from the 1510s in "Earliest English Diplomatic Ciphers".
Stile's cipher turned out to be the one used in an undeciphered ciphertext I found in the Spanish archives (which was deciphered in the nineteenth century!). The condensed writing is so characteristic that the moment I saw Stile's cipher letter, I was sure it is the cipher used in the letter that I thought was Spanish. The record is now updated in "Unsolved Historical Ciphers".