Because border disputes and national incompatibilities had provided Hitler with an excuse to start the war, they remained in the minds of the Allied leaders as it drew to a close. Rationality and drawing borders by treaty hadn't worked, they told themselves; territorial wars were no longer acceptable. Better, neater solutions had to be found; the messy parts of Eastern Europe had to be made clean. When they first met in Tehran in 1943, Roosevelt, Churchill, Stalin began to discuss the problem, sometimes obliquely. There was a precedent which they all knew about: after the First World War, the Turks had transferred more than a million Greeks out of Turkish territory. They had packed them on trains, that is, together with their cows and chickens and life's savings, and sent them away, clearing the land for ethnic Turkish settlement. «While this is a harsh procedure,» noted Harry Hopkins, one of Roosevelt's advisors, «it is the only way to maintain peace.»

Quietly, Churchill agreed. As for Stalin, he had already tried the same methods on Russia's ethnic Germans, on the Tartars, and on the Karelian Finns, among others, and he came up with the plan: he simply proposed to keep those territories he had acquired in 1939 and 1940 — the Baltic states and eastern Poland, as well as the Bukovina and Bessarabian provinces of Romania — and to deport anyone who no longer belonged. Although those were lands acquired by invasion and collusion — according to the secret Molotov-Ribbentrop pact between the Soviet Union and Nazi Germany — America and Britain agreed to let Stalin have what he wanted.

At Potsdam, in 1945, Stalin claimed Konigsberg and the northern half of East Prussia too: almost no Germans, he lied, were left in East Prussia anyway.