The US was waging an undeclared war against Germany in the Atlantic. US ships followed German merchant ships from Mexico, broadcasting their position to the British navy. My own grandfather was in the Neutrality Patrol in the Atlantic, where they attacked German naval vessels. The best-known incident was that of the Reuben James, where the US Navy ship positioned itself between the location of a known wolf pack and a convoy packed with war materiel headed for Britain. USS Kearny dropped depth charges on German U-boats while at peace. President Roosevelt announced his infamous "shoot-on-sight" order: that German U-boat "very presence in any waters which America deems vital to its defense constitutes an attack. In the waters which we deem necessary for our defense, American naval vessels and American planes will no longer wait until Axis submarines lurking under the water, or Axis raiders on the surface of the sea, strike their deadly blow—first."

What defense? We were chilling on our side of the Atlantic, why's our defense necessary in the middle of the ocean? And FDR just said their mere presence is grounds to open fire.