Israel was fighting in Lebanon before there was a Hezbollah. There was an invasion in 78. The invasion in 82 was especially egregious because it was basically a Gulf of Tonkin episode.
en.wikipedia.org
This wiki page, incidentally, contains an interesting sentence. It seems not terribly neutral, which is odd for wikipedia, especially for this particular conflict. Anyway, it's sourced to a book by Israeli historian Benny Morris, so it's probably not complete BS. Anyway, I'm not going to opine about what happened in that conflict, but I think it's fair to say that Israel's incursions into Lebanon were neither entirely (or even primarily) in self-defense, nor were they particularly just.