Complex sentence: When the German tanks moved to face-hardenned armour, the appropriate APCBC was not available, and by the time it was, German tanks had adapted specifically to counter it.
Split into simpler sentences: When the German tanks moved to face-hardenned armour, the appropriate Armour Piercing Capped and Ballistic Capped (APCBC) ammunition was not available. By the time it was, German tanks had adapted specifically to counter it.