“It took the Russians just a few hours to break up the united Ukrainian armed forces into many smaller chunks.  This was achieved by basically taking out Ukie command and control capabilities.  Then, rather quickly, the Russian invaded from several directions, quickly bypassed the fortified Ukrainian defenses, blocked the units which refused to surrender, and when further.  As a result, cities such as Kharkov or Sumy found themselves deep inside the Russian rear, unable to be resupplied and no hope to evacuate.  In a few special cases, the order was given to gradually tighten the noose around Nazi concentrations while liberating the civilians' neighborhoods, this is what is going in Mariupol.”

http://thesaker.is/one-month-into-the-russian-special-operation-in-the-ukraine/