If the United States breaks its security ties with Europe before the continent builds up its own defenses, Vladimir Putin may seize the window of opportunity to attack a Baltic neighbor and demonstrate that NATO's collective defense guarantee is worthless. That scenario - not high-probability but "entirely realistic" - is laid out in a new Carnegie Endowment assessment, "Hvylya" reports, citing the analysis by Eugene Rumer.
Rumer argues that while conventional wisdom holds Russia cannot attack another European country while bogged down in Ukraine, conventional wisdom also held in 2021 that a full-scale invasion of Ukraine was unlikely. Even Ukrainian President Volodymyr Zelensky "referred to warnings about the impending Russian assault as panic," he notes. Putin may calculate that "time is not on his side, as Europe is racing to rearm," and decide to act before the window closes.
The Trump administration's actions have made this scenario more plausible. Washington's National Security Strategy, harsh rhetoric toward European allies, and "repeatedly stated intentions to annex Greenland, if necessary, by military means" have signaled that allies "can no longer count on the United States' pledge to come to their defense," the analysis states.
A transatlantic divorce before Europe has solved the problem of deterring Russian nuclear threats without the U.S. nuclear umbrella "would create a window of opportunity for Putin to pursue his ambitions, while hiding behind Russia's nuclear shield," Rumer writes. Putin's record of nuclear saber-rattling against a non-nuclear state - Ukraine - demonstrates this is not an abstract concern.
The new geography of the NATO-Russia confrontation compounds the danger. Russian advanced weapons are forward-deployed in Belarus and the Kaliningrad exclave, which is surrounded by NATO members Lithuania and Poland. With Russia's depleted conventional forces pushing Moscow toward greater nuclear reliance, and its 2024 doctrine elaborating scenarios for escalation, the proximity of nuclear-capable assets on both sides turns any localized crisis into a potential nuclear one.
In December 2025, NATO Secretary General Mark Rutte warned allies to prepare for a war with Russia within five years. Rumer frames this not as rhetoric but as a reflection of the post-war reality in which Russia's outcome from the Ukraine conflict "is unlikely to make Russia more secure" - and a dissatisfied, nuclear-armed Russia with depleted conventional forces may prove more dangerous, not less.
Also read: Baltic Region Broke Free From Russian Energy in Two Years: Why It Remained Vulnerable.