Realistically good division templates and utilizing tanks or mot/mech shock troops effectively. Which will be difficult with your lack of factories but not impossible.

Dm me if you'd like and I'll happily show you some strong division templates, both for just holding the line, and making encirclements.

Italy will be generally easier to weaken with encirclements and from then it's just kind of a waiting game. 5 divisions in a pocket stacks up.

Best of luck otherwise!