The use of the letter E became mandatory in 1942 due to the Great Patriotic War. Historian Evgeny Pchelov, head of the department of auxiliary historical disciplines and archaeography at the Faculty of Archives and Documentary Science of the Russian State University for the Humanities, told socialbites.ca.
The letter Yo was not in the original Slavic alphabet, since there was no “sarcastic” pronunciation in Old Russian. It gradually emerged, and by the end of the 18th century, a special letter was created to convey this sound, which was not necessarily used. It became mandatory only in 1942, during the reign of Joseph Stalin, when the Great Patriotic War was ongoing.
“A war is going on. Imagine a map of the territory on which the settlement of Kremnevo is located. How should it be read, Kremnevo or Kremnevo? There are many people in the army who need to be considered, rewarded, buried. What to call a person: Eskov or Yoskov, Shmelev or Shmelev? In battle you need absolute certainty. If you have two villages nearby, one of which is named after Yo, the commander must clearly know what exactly he needs to take or defend. On German maps, all Russian names containing the letter E are written directly with the letter E – and this is such a letter in the German language although it is not,” said the historian.
This rule was only revoked in 1956, leaving E only in proper nouns and in sentences where E and E are indistinguishable in meaning.
About what the Russian language was like before and the invention of the letter E material “socialbites.ca”.