The attack on Pearl Harbor
was neither the U.S.' first armed conflict leading to WW II, nor the last Axis attack on American soil.
On December 12, 1937, Japan, then at war with China, sank a U.S. Navy gunboat
in the Yangtze river. On April 10, 1941, a U.S. Navy destroyer
fired a depth charge at a German submarine that was preparing to attack a convoy it was escorting. On May 21, 1941, a German submarine sank a U.S. commercial ship
(after allowing its crew to evacuate.) In September, 1941 a U.S. Coast Guard cutter patrolling Greenland captured a German ship.
On October 31, 1941, a German submarine sank a U.S. Navy destroyer.
There were numerous minor attacks
on North America. Japanese submarines shelled an oil field
near Santa Barbara, California (fueling a later scare of an attack on Los Angeles.)
In Oregon, Fort Stevens was shelled by a Japanese submarine;
the fort's gunners were commanded not to return fire, lest they assist the sub's aim. In the first aerial bombing of the contintental U.S., a Japanese plane dropped two incendiary bombs
in southwestern Oregon, intending to start a forest fire. Japan captured and held two Aleutian islands
for about a year.
And, late in the war, Japan loosed thousands of fire balloons
toward the U.S.' west coast. At first it was feared they were being launched on American soil; Batman-like forensics ultimately determined exactly which beaches in Japan the sandbags came from. While the balloons did some minor damage, it was covered up in the press to avoid giving any appearance of the attacks' effectiveness.
Germany placed the Dusquene Spy Ring
, and later attempted the ill-fated sabotage operation Operation Pastorius.