In 1941, the US became involved in an undeclared war in the Atlantic against which force?

In 1941, the United States became involved in an undeclared war primarily against German U-boats, which were a significant threat in the Atlantic Ocean during World War II. U-boats were German submarines that targeted Allied shipping routes, aiming to disrupt supply lines between the United States and Europe. This conflict escalated as U-boats began attacking American merchant ships, leading to increasing tensions and engagements between the US Navy and German forces.

The key aspect of this undeclared war was the protection of American shipping and support for Allied nations, as the US was aiding nations like Britain and the Soviet Union through programs such as Lend-Lease. As German U-boats intensified their assaults, the US Navy began to take active measures, including deploying naval escorts and engaging U-boats directly, marking a shift in US involvement before officially entering World War II after the attack on Pearl Harbor later in 1941.

The other options do not capture this critical aspect of US involvement in the Atlantic during 1941.