From Putin's speech announcing the SMO

Despite all that, in December 2021, we made yet another attempt to reach agreement with the United States and its allies on the principles of European security and NATO’s non-expansion. Our efforts were in vain. The United States has not changed its position. It does not believe it necessary to agree with Russia on a matter that is critical for us. The United States is pursuing its own objectives, while neglecting our interests.

Of course, this situation begs a question: what next, what are we to expect? If history is any guide, we know that in 1940 and early 1941 the Soviet Union went to great lengths to prevent war or at least delay its outbreak. To this end, the USSR sought not to provoke the potential aggressor until the very end by refraining or postponing the most urgent and obvious preparations it had to make to defend itself from an imminent attack. When it finally acted, it was too late.

As a result, the country was not prepared to counter the invasion by Nazi Germany, which attacked our Motherland on June 22, 1941, without declaring war. The country stopped the enemy and went on to defeat it, but this came at a tremendous cost. The attempt to appease the aggressor ahead of the Great Patriotic War proved to be a mistake which came at a high cost for our people. In the first months after the hostilities broke out, we lost vast territories of strategic importance, as well as millions of lives. We will not make this mistake the second time. We have no right to do so.