Former Navy Owada Communications Unit

The Owada Communications Unit (海軍大和田通信隊) was the Imperial Japanese Navy's most critical signals intelligence installation during the Pacific War. Established in 1936 (Showa 11) in what was then Owada Town, Kitaadachi District, Saitama Prefecture — now straddling the border of Niiza City, Saitama and Kiyose City, Tokyo — the facility was purpose-built as a receiving and interception station for monitoring foreign wireless communications across the Asia-Pacific region.

The site was chosen on the Musashino Plateau for its exceptional radio reception conditions: flat terrain, minimal electromagnetic interference from railways and urban development, and stable atmospheric conditions. The facility covered approximately 1.2 million square meters, with antenna arrays extending approximately 1 km east-west and over 2 km north-south across three municipalities — Niiza, Kiyose, and Higashikurume.

Originally established as a subordinate facility of the Tokyo Naval Wireless Telegraph Station, the unit was redesignated as the "Tokyo Communications Unit Owada Detachment" in 1937. With the outbreak of the Pacific War in December 1941, the facility was elevated to independent status as the "Owada Communications Unit" (大和田通信隊), reflecting its critical importance to naval intelligence operations. The unit's staff included specially recruited Nisei (second-generation Japanese-American immigrants) capable of understanding English-language plain-text intercepts. The installation housed 23 large receivers and 200 small receivers for comprehensive signals monitoring.

The Owada unit's wartime achievements placed it at the very center of Japan's most consequential military events:

1. Pearl Harbor (December 8, 1941): The station received the famous "Tora Tora Tora" (トラ・トラ・トラ — "Tiger Tiger Tiger") Morse code transmission confirming the successful surprise attack on Pearl Harbor, as well as the American plain-text message "AIRRAID ON PEARL HARBOR X THIS IS NOT DRILL."

2. B-29 Tracking (1944–1945): As the strategic bombing campaign intensified, Owada personnel systematically intercepted B-29 bomber communications from bases on Tinian and Saipan, identifying individual aircraft by their specific call signs and unit numbers.

3. Atomic Bomb Detection (August 1945): Owada is reported to have noted the aircraft that would drop the atomic bombs — Enola Gay and Bockscar — as unusual planes operating near the Tinian airfield. After the Hiroshima bombing, it traced the call sign used in a coded message sent from over the city to an aircraft that had taken off from Tinian. Whether the unit understood that the planes carried atomic bombs is not known.

4. Potsdam Declaration Reception (July–August 1945): The unit intercepted the Allied broadcast of the Potsdam Declaration, which demanded Japan's unconditional surrender. This made Owada one of the first Japanese military facilities to receive the terms that would end the war.

Thus the Owada Communications Unit symbolically bookended Japan's Pacific War — receiving confirmation of the opening attack at Pearl Harbor and the final Allied ultimatum that led to surrender.

After Japan's defeat, the facility was transferred to the Central Meteorological Bureau (now Japan Meteorological Agency) on August 24, 1945, and then handed over to the U.S. Army 1st Cavalry Division on September 13, 1945. When the Korean War broke out in 1950, the U.S. Army Signal Corps began operations at the site. It was transferred to U.S. Air Force management in 1964 and placed under the 374th Airlift Wing at Yokota Air Base in 1992.

Today, the central facility continues to operate as the USAF Owada Communication Site (FAC 3056), jointly managed by the Japanese Ministry of Defense and U.S. forces. The Higashikurume section was redeveloped into housing complexes. Surviving physical evidence includes Imperial Navy boundary stones marked "海軍用地" (Naval Territory) in the Kiyose farmland, and original gate pillars visible within the U.S. facility perimeter. No comprehensive memorial or museum exists at the site.