Check out this excerpt from an interview at the Grayzone with Swiss Intelligence officer and NATO advisor, Jacques Baud:

JACQUES BAUD: “I think we have to understand, as you know, that the war in fact hasn’t started on 24 February this year… what led to the decision to launch an offensive in the Donbas was not what happened since 2014. There was a trigger for that…

The first is the decision and the law adopted by Volodymyr Zelensky in March 2021—that means last year—to reconquer Crimea by force…

(And,also,) the intensification of the artillery shelling of the Donbas starting on the 16th of February, and this increase in the shelling was observed, in fact, by the Observer Mission of the OSCE [Organization for Security and Co-operation in Europe], and t hey recorded this increase of violation, and it’s a massive violation. I mean, we are talking about something that is about 30 times more than what it used to be… On the 16th of February you had a massive increase of violation on the Ukrainian side. So, for the Russians, Vladimir Putin in particular, that was the sign that the operation—the Ukrainian operation—was about to start.

And then everything started; I mean, all the events came very quickly. That means that if we look at the figures, you can see that there’s…. a massive increase from the 16th-17th, and then it reached kind of a maximum on the 18th of February, and that was continuing.

… And that’s why, on the 24th of February when Vladimir Putin decided to launch the offensive, it could invoke Article 51 of the UN Charter that provides for assistance in case of attack.” (“US, EU sacrificing Ukraine to ‘weaken Russia’: fmr. NATO adviser“, The Grayzone)

WtR