Made a quick calculation about the Russian strateig objective in east ukraine.
Within the black area it is possible to shell the residental areas of Donyeck with NATO supplied weapons, as its happened in the past nine years.
It means it won't be possible to restore the normal civilian peace conditions in the million residents city.
And the area required to establish a deep enought defense as well.
Russia can't start any other attack direction before clean the black area of all long range NATO supplied artillery.
At the moment if the number of forces decreased around Donyeck the Ukrainans will start to push hard into the city.
It means as soon as Donyeck secure Russia can do whatever required to finish the war, say start a front towards kiew, liviv or whatever is they wish.
Problem is the area around Donyeck is the most fortified area on the surface of earth, the whole NATO spent good 8 years to establish the best fortifications possible.