In May 1945, the end of the second world war in Europe brought Soviet power all the way to the streets of Berlin. The Red Army had fought its way there as part of the wider Allied effort to defeat Nazi Germany. Now, 80 years on, the end of the Russo-Ukrainian war could enable Moscow to project its power westward once again.
How would that happen? Through some kind of peace accord between Ukraine and Russia — organised under American pressure — that would end hostilities in the short run but reward Russian aggression and leave open the chance of renewed conflict once Moscow reconstitutes its forces.
While the chances of Russian tanks rolling westward are (probably) limited, Moscow is already carrying out cross-border assassinations, cyber interventions, sabotage and other acts of violence short of full-scale military attack. Those would probably intensify, raising the chances of escalation. Worse, any subsequent move westward by Russia would take place in confrontation, not in alliance, with western European democracies — and in the dangerous context of US disengagement from Europe.