> The Pentagon should have recognized that the Eastern expansion of NATO would collide with the national security interests of Russia, and that war would be the inevitable consequence.

NATO is absolutely zero threat to Russia, and Russia knows it. Finland joined and Russia shrugged, and has since even removed many troops from that border because it knows NATO will not attack.

What matters is the national security interests of Ukraine.

Russia is a massive threat to the national security interests of Ukraine, and Ukraine really wants to join NATO to be safe from Russia. Russia knew that if it wanted to invade and conquer Ukraine, a souvereign country, it would have to do soon because it would not be possible anymore after Ukraine joined NATO.

Russian security interests, fuck off. Neither Ukraine nor NATO is a threat to Russia.

Ukraine's security interests, those are very obviously threatened.