The continental United States has never been attacked by a foreign air force, with one crazy exception. On September 9, 1942, a floatplane launched from a Japanese submarine attacked the small logging town of Brookings, Oregon, dropping incendiary bombs.
The Imperial Japanese Navy was one of the most formidable sea forces in World War II. At the time of the Pearl Harbor attacks, it was the most powerful navy in world, which allowed the empire to dominate the western Pacific in the early years of the war. They had the heaviest and most armed battleships ever built, the sister ships Yamato and Musashi. Their naval aviation was second to none at the beginning of the war, and it took years before the United States could effectively counter the nimble and deadly Mitsubishi A6M Zero. And while the famous German U-boats were the most effective submarine fleet of WWII, the Japanese constructed the largest submarines of the war, many of which carried their own aircraft. The largest of the Imperial Navy, the I-400-class, could carry three floatplane bombers, underwater and undetected, and had a range that allowed it to travel around the world one and a half times (and this was before nuclear power - these subs ran on diesel engines).
But it was one of the smaller B1-type submarines, I-25, that carried out the only air attack on the continental United States in the war. During its first patrol in late 1941, the sub patrolled the waters north of Hawaii during the Pearl Harbor attacks, and even went as far east as the mouth of the Columbia River at the border of Oregon and Washington. Its second patrol took the sub on missions in Australia and New Zealand, launching its Yokosuka E14Y "Glen" aircraft on reconnaissance flights over Sydney Harbor, and Port Phillip Bay in Melbourne. Warrant Flying Officer Nobuo Fujita later flew over Wellington and Auckland, New Zealand. On the third patrol, the submarine bombarded Fort Stevens in Oregon from 10 miles off the coast.
I-25's fourth patrol sent the sub back to the Pacific Northwest. On September 9, 1942, Fujita launched the Glen aircraft carrying two 168-pound incendiary bombs. Their mission was to drop the bombs over the forested region along the Oregon/California border in an attempt to start devastating forest fires. The Japanese had also launched thousands of firebomb-loaded weather balloons with the same intention (some were discovered as far east as Michigan). One of Fujita's bombs managed to land on Mount Emily, east of Brookings, Oregon, starting a small blaze. Due to wet conditions, and a rapid response from the U.S. Forest Service (his plane had been spotted during the attack), the fire, later dubbed the Lookout Air Raid, did little damage. Weeks later, I-25 launched the plane again for a less successful mission. Fujita reported seeing flames but the attack went unnoticed.
Fujita managed to survive the end of the war, and opened a hardware store near Tokyo, although it later went bankrupt. He later worked at a wire company and rarely spoke of his military service. His family had no idea of his attack on the U.S. mainland until he was invited to Brookings in 1962. He visited the town with his family's 400-year-old samurai sword with the intent of presenting it to the town as an apology for the attack. If the town did not accept his apology, Fujita, a reserved and humble man, had planned to commit ritual suicide (seppuku) with the sword. "He thought perhaps people would still be angry and would throw eggs at him," his daughter Yoriko Asakura told The New York Times. "If that happened, as a Japanese, he wanted to take responsibility for what he had done."
Instead, the town welcomed him with open arms (local churches and businesses raised the money for his visit in 1962). He later paid for several Brookings students' trips to Japan, as well as donating money to the town's library for children's books on Japan. He visited the town three more times in his later life and planted trees at the bombing site. His family's sword was displayed in the Brookings' city hall and is currently displayed in their library. He was made an honorary citizen of the town shortly before his death in 1997, and some of his ashes were buried at the bombing site.