Japanese Defense Minister Koizumi Shinjiro and U.S. Secretary of Defense Pete Hegseth met in Washington on January 15 to solidify Japan-U.S. security ties. It was the fourth discussion between Hegseth and Koizumi since the latter became defense minister in October. 

In a Department of Defense (DoD) readout of the meeting, it was announced that the Koizumi and Hegseth “agreed to continue upgrading alliance command-and-control architectures, make bilateral training and exercises more realistic, improve alliance force posture and presence – including in Japan’s Southwest islands.” 

Tensions between Japan and China have increased in recent months, following Japanese Prime Minister Takaichi Sanae’s remarks in November that suggested Japan could become involved militarily if China attacked Taiwan. Chinese air and sea exercises near Taiwan in December are a stark reminder of the threat that China poses directly to Taiwan and indirectly to Japan, especially Japan’s southwestern islands. Although U.S. support for Japan in the ongoing crisis has been less forceful than it could be, Japan will do its best to try to strengthen security cooperation with the United States. 

Expanded joint training across Japan’s Southwest (Nansei) Islands is one of the ways that Japan and the United States are strengthening their security cooperation. In the opening statement, Hegseth said, “Strengthening our force through realistic training and exercises in Japan, across the First Island Chain, again, is the kind of operational demonstration we need to be capable of showing.” 

Similarly, the Japanese Ministry of Defense (MoD) summary concluded that the allies agreed to make it a priority to work on the expansion of “more sophisticated and practical joint drills in various locations, particularly in the Southwest region.” 

This is already happening. In 2023 the U.S. Marine Corps (USMC)-Japan Ground Self-Defense Forces (JGSDF) annual Iron Fist exercise was moved from the United States to Southwest Japan. In 2024, the annual USMC-JGSDF exercise Resolute Dragon deployed a mobile radar to Yonaguni Island – Japan’s westernmost island, located about 110 kilometers east of Taiwan. In 2025, the Navy/Marine Corps Expeditionary Ship Interdiction System (NMESIS) was employed for the first time in Resolute Dragon in Japan’s southwest region, and a forward arming and refueling point (FARP) was established for the first time on Yonaguni Island as part of a joint exercise between the USMC and JGSDF.

Beyond cooperation with the United States, Japan is also strengthening its own capabilities on the southwestern islands. Last November, Koizumi visited a JGSDF base on Yonaguni Island. He reiterated the MoD’s plan to deploy medium-range surface-to-air missiles, an upgraded variant of the Type 03 Chu-SAM missile system that can intercept cruise missiles. He also traveled to Miyako Island and Ishigaki Island and discussed progress on the construction of underground shelters. 

Efforts to strengthen defense of the Southwest Islands have been ongoing. The JGSDF first established a camp on Yonaguni Island in 2016 to host a Coast Observation Unit. A Japanese Air Self-Defense Force (JASDF) squadron was deployed in 2022, and the JGSDF was augmented with an electronic warfare unit in 2023. In addition to the missile system, Japan wants to deploy an anti-aircraft electronic warfare unit capable of disrupting enemy aircraft radar in 2026. 

Japan established JGSDF bases on Miyako Island and Amami-Oshima Island in 2019, and on Ishigaki Island in 2023. The JSDF is also constructing an air base on Mageshima Island, but its completion will be delayed until 2030. These bases bolster Japan’s air defenses. 

There is also discussion of deploying long-range missiles, and the Japanese government is discussing deploying a JASDF mobile warning and surveillance radar unit to Kita-Daitojima Island. 

In addition to increasing Japan’s ability to monitor and respond to Chinese activities, it is hoped that the stationing of missile units – including surface-to-ship missiles, surface-to-air missiles, and surface-to-surface missiles – in the Southwest Islands will deter China from launching a military campaign. 

However, the militarization of the islands faces local opposition. Residents are concerned that they are being drawn into a geopolitical conflict by hosting JSDF bases and have urged leaders in Tokyo to focus on diplomacy with China.  

The reality is that maintaining peace across the Taiwan Strait is not under Tokyo’s control. Last December, JSDF planes were targeted by radar from Chinese aircraft over international waters and Chinese and Russian strategic bombers flew on a route toward Tokyo. During the December 2025 military exercises encircling Taiwan, Chinese military bombers and fighter jets passed between Okinawa Island and Miyako Island to advance into the Pacific Ocean. 

Chinese Coast Guard vessels navigated in Japan’s contiguous zone (the 22-km wide zone outside a country’s territorial waters) for 356 days in 2025. That edges out the previous record of 355 days in 2024.

Koizumi understands the importance of local sentiment. He visited Okinawa for the second time as defense minister in early January. While he was respectful of the burdens placed on the Okinawan people, he offered no concrete suggestions to improve their situation.

Additional outcomes from the January Koizumi-Hegseth meeting include boosting joint production of defense equipment, including air-to-air missiles and surface-to-air interceptors, maintenance and repair of U.S. military ships and aircraft, and supply chain resilience, including of critical minerals. Koizumi pushed to hold the next Japan-U.S. Defense Industrial Cooperation, Acquisition, and Sustainment (DICAS) consultation meeting. 

Before Washington, Koizumi also stopped in Hawai’i, where he met commander of the U.S. Indo-Pacific Command, Adm. Samuel Paparo, and attended the Honolulu Defense Forum. In Los Angeles, where he held talks with drone makers and visited a drone manufacturer.