The Japanese Navy tried to destroy the Golden Gate Bridge with torpedoes

In the wake of the Japanese attack on Pearl Harbor in December 1941, the American people were left stunned and unsure of what the near future would hold. It left the public on the homefront worried and paranoid about spies, saboteurs, and possible future attacks on the homeland. 

In the months and years to come, several incidents occurred that highlighted the fear and paranoia among Americans. In February 1942, air defenses around Los Angeles lit up the dark skies in response to what they thought was a nighttime air raid. Later that same year Japanese fire bombs killed six in Oregon in an attempt to trigger a massive wildfire. 

These events demonstrate that fears of Japanese attacks may have been overblown, but they weren’t entirely unfounded. One Japanese attack on a major metropolitan area went completely unnoticed for the duration of the war, and it came just three weeks after the bombing of Pearl Harbor.

Imperial Japanese Navy submarines approached the Golden Gate Bridge in San Francisco, fired a torpedo and withdrew. No one found the torpedo until after World War II ended. 

In December 1941, immediately following its surprise attack on Hawaii, Japan launched a massive submarine campaign against the U.S. West Coast, trying to capitalize on its surprise and interfere with merchant shipping. Increased submarine attacks would also intimidate the American populace. 

Japanese subs also hit shore targets, bombarding islands and fortifications with their deck guns before retreating under the waves. Japanese incendiary bombs from planes and balloons not only targeted the forests of Oregon, but the entire West Coast from Canada to Mexico. December 1941 also saw Japanese subs outside of a major American landmark, the Golden Gate Bridge.

There were nine Japanese subs dispatched to the West Coast to attack merchant shipping in the weeks following the attack on Pearl Harbor. They concentrated on major cities, rivers, and military installations. One sub, I-15, was sent to San Francisco. It was a large vessel, complete with a catapult-launched reconnaissance seaplane.

I-15 surfaced near the Farallon Islands off the California coast to recharge batteries and air out the boat. It stayed in the area for a few more days, but failed to intercept U.S. shipping. A plan to bombard American coastal areas on Christmas was delayed and then canceled due to low fuel supplies aboard the boats. 

They all began to return home, but I-15 decided to take a potshot at the Golden Gate Bridge before departing for waters closer to home. It must have been I-15 because no other submarines were in the area. 

The submarine apparently approached the area, fired one 6,000-pound Type-93 “Long Lance” torpedo at the bridge and withdrew. Hitting the bridge would have been a coup for the crew, it was very new at the time and was then the longest suspension bridge in the world. If the torpedo had hit one of the towers, the entire bridge might have been compromised. The torpedo hit Marshall’s Beach, where it stayed for the rest of the war. 

It wasn’t until 1946 that the torpedo was actually found by Americans. It was still live and half buried in a sand bank close to the bridge. It was a surprise and a mystery – but one researcher knew exactly how it got there. A U.S. Navy demolitions squad neutralized the warhead.