“It’s a very interesting phrase; it was never used before. You look back, you look at Iraq, which was totally unprovoked, nobody ever called it ‘the unprovoked invasion of Iraq.’

Well, Chomsky is really stupid. The term "unprovoked" is a reference to international law. This term has been around for more than 70 years. A provoked war is considered self-defence and is authorized by the United Nations Charter. An unprovoked war is considered a war of aggression, an unlawful intervention in other countries soverheignity.

The Iraq is not an example of an unprovoked war because both the coalition and Iraq were already in war before the 2001 invasion. The war was in fact provoked when Saddam Hussein invaded Kuwait in the 90s, the first gulf war never ended because there was no peace treaty.

It’s just a well-documented fact that the US and its allies provoked this war in a whole host of ways, from NATO expansion to backing regime change in Kyiv to playing along with aggressions against Donbass separatists to pouring weapons into Ukraine. There’s also an abundance of evidence that the US and its allies sabotaged a peace deal between Russia and Ukraine in the early weeks of the war in order to keep this conflict going as long as possible to hurt Russian interests.

None of this is considered Casus Belli, specially for a third non-involved party like Russia.