The outcome of the Ukraine war will determine the safety of the wider region, Angela Stent and Fiona Hill warn.
Putin's "appetite for expansion would not stop at the Ukrainian border" if Russia wins, they said in a new op-ed.
They warned that nearby countries like Poland and Finland could face attack if Russia prevails.
"Even now, after a year of carnage, Putin is still convinced he can prevail," Stent and Hill wrote in a new op-ed for Foreign Affairs.
Putin has often pointed to Russia's imperial past when offering justifications for the war in Ukraine, at one point likening himself to Peter the Great.