What was president Franklin d Roosevelt greatest contribution while the nation recovered from an economic disaster and faced another potential war in Europe ?

President Franklin D. Roosevelt's greatest contribution during the nation's recovery from economic disaster and the looming war in Europe was his leadership through the Great Depression and World War II. He implemented the New Deal, a series of programs and reforms aimed at stabilizing the economy, providing relief to the unemployed and stimulating recovery. Roosevelt's policies created numerous public works projects, established social welfare programs and introduced regulatory measures to reform the financial system.

Furthermore, his leadership during World War II was pivotal. Before the U.S. officially entered the war, Roosevelt supported the Allied powers through various lend-lease programs and provided critical aid to countries fighting against Axis aggression. After the attack on Pearl Harbor, Roosevelt led the country through the war effort, mobilizing the nation's resources for the war, including the manufacturing sector and military production, while boosting morale and maintaining unity among Americans. His diplomatic skills also played a crucial role in shaping the post-war world order.