Final answer:
Stalin was heavily protected on his way to the Potsdam Conference due to his critical role in geopolitical events and the significant threats he faced as the key leader of the USSR during tumultuous times. He had a history of strategic military and political actions that increased his influence but also his potential enemies. These factors warranted extraordinary security measures to ensure his safe participation in crucial post-war negotiations.
Step-by-step explanation:
Extraordinary measures were taken to protect Stalin on his way to the Potsdam Conference due to the fact that he was a key figure in the geopolitics of the time and had many potential threats against him. His regime's survival relied on his leadership, and his previous actions had secured both a certain level of stability within the USSR and hostility from outside entities. Stalin, having been instrumental during strategic military conflicts and political maneuvers—ranging from the decisions during the Molotov-Ribbentrop pact periods, to the purges of the Red Army, to the shaping of Eastern European politics post-World War II—was a critical player on the world stage.
The security surrounding Stalin was also influenced by the atmosphere of danger propagated through the Stalin cult, which, as Plamper noted, had varied portrayals of Stalin being in danger in Pravda to garner public support. The Potsdam Conference was a crucial moment for determining the post-war structure of Europe, and Stalin's presence as a central figure to these negotiations was therefore heavily protected.