U.S. President Joe Biden’s sudden appearance in Kyiv’s presidential palace on Monday morning was intended first as a morale booster for shellshocked Ukrainians in the midst of a bleak winter of power outages and a bitter war of attrition.

But it was also the first of several direct challenges on this trip to Russian President Vladimir Putin, who a year ago this week believed the Ukrainian capital would become Russian-controlled territory again in a matter of days, moving Putin closer to his ambition of restoring the empire of Peter the Great.

"Putin’s war of conquest is failing,” Biden declared from the palace, his very presence there, alongside Ukrainian President Volodymyr Zelenskyy, meant to symbolize Russia’s failure to take a capital that today remains brimming with life, its restaurants overflowing even as warning sirens blare.