Within a few hours of the attack on Pearl Harbor on December 7, 1941--by 4 pm that Sunday afternoon--barbed wire was going up along the beaches of Southern California, and machine guns were in place in the sand. Wish I had a picture of that! Apparently, the Army or civil defense agencies were convinced that a Japanese fleet was en route to the mainland and could appear at any moment.
C. Scott Littleton, who was 8 years old at the time, remembers this in his memoir 2500 Strand: Growing up in Hermosa Beach, California during World War II. The book title was his address; the closest machine gun emplacement was at the foot of 25th Street in Hermosa. It disappeared after a few days.
The barbed wire stayed longer. Littleton recalls gunfire between 8 and 10 pm every night. A piece of debris or worthless old rowboat would be towed out to sea, searchlights would fasten on it, and the GIs used it as target practice.
Remember the "Battle of Los Angeles"--the basis for the movie 1941 ? Something set off the alarms around 3 am, a couple of months after Pearl Harbor, and sent the city into a panic. Littleton followed his parents outside to see what the machine gunners were shooting at and saw planes in the sky. An attack by Imperial Japan? Not even. It appears that a plane was shot down near Vermont and 180th--but it was probably an American plane with an American pilot, defending the homeland.