Related Question on Metaculus:
In late 2021 and early 2022, several Western governments began publicly expressing concern about a potential Russian invasion of Ukraine outside the previously occupied territories in the Donbas and Crimea. The New York Times reported on January 14, 2022:
“If Putin invades Ukraine with a major military force, U.S. and NATO military assistance — intelligence, cyber, anti-armor and anti-air weapons, offensive naval missiles — would ratchet up significantly,” said James Stavridis, a retired four-star Navy admiral who was the supreme allied commander at NATO. “And if it turned into a Ukrainian insurgency, Putin should realize that after fighting insurgencies ourselves for two decades, we know how to arm, train and energize them.”
NBC reported on February 8, 2022:
“Even with the disparity of forces, they can move in very fast and quite successfully, but then holding it would be a disaster,” said Andriy Zagorodnyuk, a former Ukrainian minister of defense who left office in 2020. Zagorodnyuk said that Ukraine’s military is fully aware of its weaknesses when it comes to a conventional face-to-face war and that plans for an insurgency or guerrilla-style resistance movement led by Ukraine’s military are now the government’s primary strategy — even if the Ministry of Defense has not stated so publicly.
Others have been skeptical that a "serious" Ukrainian insurgency will take place, for instance on January 26, 2022, Richard Hanania predicted "Washington is now deluding itself into believing that it can help facilitate an insurgency in Ukraine. This will not happen."