The ranks of the critics at the pinnacle of power remain limited, spread across high-level posts in government and state-run business. They believe the invasion was a catastrophic mistake that will set the country back for years, according to ten people with direct knowledge of the situation. All spoke on condition of anonymity, too fearful of retribution to comment publicly.

So far, these people see no chance the Russian president will change course and no prospect of any challenge to him at home. More and more reliant on a narrowing circle of hardline advisers, Putin has dismissed attempts by other officials to warn him of the crippling economic and political cost, they said.

Some said they increasingly share the fear voiced by U.S. intelligence officials that Putin could turn to a limited use of nuclear weapons if faced with failure in a campaign he views as his historic mission.