Today the office of Ukrainian President Petro Poroshenko released via Twitter important details about the organization and structure of Russia’s occupying army in Southeastern Ukraine. The order of battle (ORBAT) information is clearly derived from a lot of intelligence, especially SIGINT (I say this as someone who used to do ORBAT intelligence for a living: this is well done).
Since most of my readers know neither Russian or Ukrainian, I’m passing on what Kyiv has released today in English. The translation isn’t great but it works. I’m providing comments below since most normals are not well acquainted with the nuances of Russian military organization.
Russian Military Command, South-East Ukraine (Novocherkask):
Commanding Officer (CO): GenCol A N. Serdyukov 
1st Army Corps (“Donetsk People’s Republic” Military), HQ: Donetsk