You dont take Kharkiv with 10,000 troops unless the opposing forces withdraw in blind panic...... I guess you cant rule out the possibility altogether but that was never likely and not the plan.
As part of a war of attrition you open a new front which draws reserves up from rear areas as a response, ideally you draw in some large formations of opposing forces into your own artillery and glide bomb range then hit em hard.
Rinse and repeat till there arent any significant reserves remaining
