“Secret inks,” intercepted telegraphs and even postage stamps fell under national scrutiny during World War I when the War Department commissioned Herbert Yardley to create the American Cryptographic Bureau, the U.S. Army’s first cipher team.
Yardley, a young telegraph operator, was recruited by War Department intelligence specialist Ralph Van Deman to initiate the new bureau, better known as MI-8, which blossomed into divisions that included code and cipher solutions and assemblage; secret inks; shorthand;, and communications, an article looking back at World War I cryptology efforts that was posted on the Army's website said.
“Every suspicious missive, military or civilian, ended up on the desks of this subsection,” the article said. "The nation’s early cryptology division examined all manner of materials, from radio and cable messages to mail, solving 50 codes and ciphers including a pivotal case involving a German spy; and its chemists developed an iodine vapor to read “secret inks.”
"It is the business of a Cipher Bureau never to allow its interests or energies to flag, for although a thousand suspicious documents may turn out…to be entirely innocent or insignificant, the very next one might be of the greatest importance," Capt.John Manley, a key member of the World War I-era bureau, said according to Army records.
Code and cipher solutions “also analyzed atypical items like postage stamps, musical scores, religious amulets, and even a pigeon's wings,” the article said.
MI-8 continued after the war as cryptology evolved, first coming under the realm of mechanical apparatus during World War II and serving as the forerunner of modern surveillance technology.