That would be north and east of the Dneiper not south and east as that would mean the entire country.
Even so, what exactly is a “small incursion?” If Canada occupied Port Roberts WA would that be okay? We could use access to Port Roberts marina.
Putin’s “minor incursion” will be to take the entire Black Sea coast including Odessa to get his land bridge to the Crimea.
The Dnieper river will be the new border between Ukraine and Russia.