1. Nazi aggression and human rights abuses: Germany's aggressive expansionist policies under the leadership of Adolf Hitler, particularly the invasion of Poland in September 1939, shocked many Americans and raised concerns about the potential consequences of unchecked German power. The reports of Nazi atrocities, including the systematic persecution and genocide of Jews and other vulnerable groups, further fueled public outrage and support for action against the Nazi regime.
2. Perceived threats to national security: The sinking of several American vessels, including the destroyer USS Greer and the passenger ship SS Athenia, by German U-boats in the early stages of the war raised fears about the security of American sea lanes and shipping. Additionally, the expansion of German control in Europe and the fall of France in 1940 prompted concerns about potential threats to the United States' own security.
3. Economic considerations: Although the United States initially pursued a policy of neutrality, it also provided considerable economic support to Great Britain and other Allied powers through programs such as the Lend-Lease Act. As the war progressed, there were growing calls from American businesses and policymakers to take more direct action to protect their economic interests and safeguard access to vital resources and markets.
4. Isolationist sentiment softening: While the United States had traditionally followed an isolationist policy, public opinion gradually shifted as news of Nazi atrocities, the plight of Allied nations, and the strategic implications of German expansionism became more widely known. Isolationist sentiments began to weaken as many Americans concluded that the war could no longer be ignored and that the United States had a moral and strategic responsibility to intervene.
5. Wartime propaganda: Both the Roosevelt administration and various pro-war organizations conducted campaigns to influence public opinion and build support for American intervention. The use of propaganda and media messaging played a significant role in shaping public perceptions of the war and creating a sense of urgency about the need for action against Nazi Germany.
It's important to note that while there was growing support for American involvement in the war, there was also significant opposition to direct intervention, especially before the attack on Pearl Harbor in December 1941. The decision to enter World War II was ultimately a complex and multifaceted one, influenced by a combination of factors that ranged from moral and ethical concerns to strategic considerations and domestic politics.