This is the biggest military defeat suffered by Russia since the second world war.
Don't be dramatic. According to information from sources close to reliable, about 1,500 soldiers controlled this entire vast territory in the Kharkov region from Russia and the LDNR. Most of which retreated in an organized manner across the Northern Donets River in order to avoid the threat of encirclement.
I am not so sure about all this. Izyum was a major battlefront many months back and it was captured by the Russians after weeks of bloody fight. Same with Kupiansk as well. And these two towns were strategically located as supply routes. Surrendering them to Ukraine in a matter of days was surprising to say the least. And the Ukrainians are now claiming that they outnumber the Russians by a ratio of 8 to 1 in Kharkov front. Where did all the soldiers vanished? They are not making gains anywhere else. Donbass front has been stagnant for many weeks and in Kherson they are on the backfoot.