@Field:
Now with an Industrial zone of 10 the USA would put 5 fighters and 5 tanks in each buy thus obliterating Germany.
Whenever you capture a Major Industrial Complex, it turns into a Minor Complex. Additionally, only the original power can restore it back to a Major Industrial Complex.
Just so you know, that shouldn’t have been possible - unless you were playing with house rules that say otherwise.
Our house rules state if you lose a Major Industrial Complex you pay the consequences.