I was 12 (earlier than ’83!) I already had Airfix figures and I was playing with them (with no rules)… I went to the UK for a trip… and in a bookshop I found this:
It was in a bookshelf between “normal” books about fishing or gardening, this would have been unbelievable in France at the time.
I still have it. …In fact I never played with it, it’s unplayable, but it was fascinating, there are ideas to think about, and it did help me to understand that wargaming could be accepted by “serious” people and not despised as a kid’s game.