During which historical event did FDR play a significant role in shaping U.S. policy?

Franklin D. Roosevelt (FDR) played a crucial role in shaping U.S. policy during the Great Depression, which was a severe economic downturn that lasted from 1929 to the late 1930s. His administration implemented a series of programs and reforms known as the New Deal, aimed at promoting economic recovery, providing relief for the unemployed, and reforming the financial system to prevent future crises.

The New Deal included initiatives like the establishment of the Social Security system, programs to stabilize agricultural prices, and the creation of jobs through public works projects. These efforts significantly altered the relationship between the government and the economy, reinforcing the idea that the federal government should take an active role in economic affairs and the welfare of its citizens.

In contrast, while FDR was president during the early part of World War II, his direct involvement in the Cold War, the Vietnam War, or the Korean War was limited, as these events occurred after his presidency ended in 1945. Thus, the Great Depression remains the defining event during which FDR's policies had the most significant and lasting impact on the United States.