NATO members, and Ukraine leaders, have been openly stating that they've been preparing to do so since 2014. I remember when Angela Merkel was saying that they wouldn't arm Ukraine, for fear of instigating a greater situation, while the US was just openly contemplating arming and training Ukraine. They all boasted as the trained and armed Ukraine's military, while Ukraine boasted of building a domestic arms development, while becoming developers of ballistic missile innovations, planning an offensive just before the media started reporting a "Russian invasion"... although that had been going on since even before 2014. With the amount of civilian casualties over the last 10 years in Eastern Ukraine, there's probably nothing left but NATO versus Russia's meat for the grinder fighting in Ukraine's Donbas region. Both sides have ignored international worries, repeatedly broke cease fire treaty and openly planned preparing for an offensive...right about now.