Back in 1967 the Israelis could not have known either. Egypt was not merely acting aggressively though. It had already broken their peace treaty, cut off Israeli shipping, massed its troops and was actively saying to the media that their plan was to destroy Israel. Maybe they were lying or just posturing. But that isn't Israel's guess to make. When an enemy swears to their destruction they had no choice but to take it seriously. Anything else would be irresponsible.
Bear in mind that Israel had to mass THEIR army to counter Egypt's, even if neither had yet engaged, For Israel this entails shutting down most of the economy as the army is made up of average citizens. It can't afford to stay mobilized for very long at full strength, the state would go bankrupt.
Regarding Lebanon, if cross-border 'raids' by non-state actors are justification for invasion, Iran is probably justified in declaring war on the US, Iraq, Afghanistan, and Israel, since each of these countries has hosted or launched terrorist attacks in Iranian territory.
What are you talking about? The PLO was carrying out raids over Israel's border with the aim of killing Israeli civilians and Lebanon did nothing to curb it. Of course that is a justification for Israel to take military action. In 2006 Hezbollah crossed the border to kill and kidnap Israelis, again without facing any Lebanese response. Why does it matter if it's a state actor or not? Hezbollah is an illegal paramilitary group that poses a significant threat to both Lebanese democracy and Israeli stability.
When did the US, Iraq, Afghanistan or Israel launch terrorist attacks in Iran?
And in fact, if Israel had waited and let Egypt attack, IMO they would have been perfectly justified in annexing Egyptian territory as part of any peace settlement.
Huh? Why? Does that mean that you think Israel is justified in retaining the West Bank, since Jordan attacked them? How about the Sinai based on Egypt's 1979 attack?
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