Oh I agree Kharkov is their northern anchor. Let them attack down roads mined with IEDs and ambushes every mile, through your reserves in hiding, who will be at their backs when the front passes through and busy at night. Get them tied up on the roads in stopped columns and destroy them with drones and long range artillery. Put up a token resistance at the front when they start their drive, pull back to secondary positions when they pound the front ones with artillery, then move back in, melt away and draw them into a series to traps along the highway to perdition. DON'T try and stop their advance in open battle, trade space for time and get them as far as you can from their supply bases, before counter attacking everywhere at one, in the front, the flanks and in the rear, using reserves to block roads in built up areas.
