Three tall towers in the shape of a triangle can be seen alongside the Hario Seto Straits, in Nagasaki, Japan. These three wireless towers transmitted the coded message that launched the attack on Pearl Harbor, triggering the Pacific War on December 7, 1941.

Previously named Old Sasebo Wireless Transmission Facility, the Imperial Japanese Navy began construction of this facility in 1918 and completed it in 1922. The Russo-Japanese War triggered a need for the strengthening of wireless communication. Its construction at the time totaled 1,550,000 yen (current value is about 25,000 million yen). 300,000 yen (current value is about 5,000 million yen) was spent on each wireless tower.

Known today as the Hario Transmitting Station, these three ferro-concrete towers in the facility stand at 446 feet. They were constructed like a chimney with the bottoms, which were 39 feet in diameter. The wireless towers were located on a regular triangle with 984 feet each side, and the ferro-concrete transmission facility, called the transmission room, was constructed in the middle. The transmission room is a huge, semi-subterranean, two-storied building with 13,520 square feet in floor space. Additionally, building structures such as an oil warehouse, a water tank, a watch house, a site of barracks, and harbor facilities are left.

This facility is famously known as the facility which transmitted the code “Climb Mount Niitaka 1208” to order an attack on Pearl Harbor. However, there are no materials regarding it and it is not clear if it really transmitted the code. Through recent studies, this facility was prized for its engineering art and wireless technology, along with its historical background. It was also designated for the important cultural asset as the modern heritage which symbolizes development of technology in Japan.

        

        

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