The Truman administration's obvious concern with the Soviet Union highlights the other important foreign policy consideration of the early Truman years. Truman inherited an increasingly difficult relationship with the Soviets from FDR. As the wartime necessity of co-operation began to wane with the decline and fall of the Nazi regime, the divergent interests of the two allies increasingly came to the fore. FDR's hopes for a stable postwar environment hinged on the ability of the United States and the Soviet Union to co-operate in managing the new world order. He recognized that the two nations, so different in history, ideology, and geography, would not see eye to eye on every issue. For example, while FDR knew that he could not prevent the Soviets from establishing a sphere of influence in eastern Europe, he remained optimistic that good relations between the United States and the Soviet Union could ameliorate the impact of the Soviet sphere. If the Soviets used restraint and were not too heavy-handed in their domination, it would not prove problematic. In practice, however, the Soviet Union proved insensitive to American concerns, especially those of the American public. FDR went to his grave hopeful that the mutual interest of the great powers in preventing another cataclysmic world war would allow them to continue the co-operation of the war years to their common benefit. It was not to be.