Why do you think that? The east of Ukraine is a flat plain, now the freeze is setting in its well suited to mechanised warfare. With no terrain boundaries they've got lots of potential to advance and cut off the land supply route, and water supply to Crimea.
Because Russia is on there border and will continue to shell the Ukraine un opposed
They are digging in for the winter
And restocking on missiles ect
The US are supplying Ukraine with sophisticated weaponary
Under the under standing that they are not used to attack Russia
??