Thank you for your response, very helpful.

I do try to find weak spots in enemy's defense and attack hexes where I have superior power.

Will motorizing my infantry troops improve my ability to exploit breakthrough?
In some cases I had tank brigades and I was able to send them in the whole, but ...

I have few hexes on a front line which have 3 regiments on each(enemy occupies all hexes on other side of front line). I do "Deliberate Attack", enemy retreats in some hex. Now units I used in attack, have no movement points to move in and they can't move back. Other units I left in the hex behind ...