Two U.S. Air Force B-52H Stratofortress bombers flew with Japanese F-35A and F-15 fighters over the Sea of Japan in December 2025, in a joint exercise held during a sharp rise in military and diplomatic tensions involving Japan, China and Russia. Japan said the flight demonstrated the readiness of the U.S.-Japan alliance after a joint Chinese-Russian bomber patrol and a disputed radar incident involving Chinese and Japanese fighter aircraft.
The exercise was significant because of its timing, but it did not itself indicate that nuclear weapons were deployed or that an armed confrontation was imminent. The B-52H is capable of delivering conventional and nuclear weapons, while the aircraft involved in the Japanese formation were conducting a bilateral training mission intended to demonstrate interoperability and readiness.
What the U.S.-Japan Exercise Involved
Japan's Defense Ministry said two B-52 bombers operated with six Japan Air Self-Defense Force fighters: three F-35As and three F-15s. The aircraft conducted the joint flight over the Sea of Japan on December 10, according to Japanese officials.
The mission came shortly after Chinese and Russian military aircraft conducted their own joint flight around Japan. Reuters reported that Tokyo described the U.S.-Japan exercise as reaffirming the allies' readiness and their opposition to attempts to change the regional status quo by force. The exercise should therefore be understood as a visible demonstration of alliance coordination rather than evidence that either country had begun combat operations.
The Radar Incident Behind the Wider Tensions
A major source of tension was an encounter on December 6 involving Japanese F-15 fighters and J-15 carrier-based fighters operating from China's aircraft carrier Liaoning southeast of Okinawa. Japan's Defense Ministry said Chinese aircraft directed radar at Japanese fighters on two occasions over international waters and described the incidents as dangerous.
The precise nature and purpose of the radar use became a matter of dispute between Tokyo and Beijing. Japan did not establish publicly that a weapon had been fired or that an attack had begun. Its concern centered on the risks created when a fighter aircraft receives radar emissions from another military aircraft and cannot reliably determine the radar's intended purpose.
In a December 10 statement, Japan's Defense Ministry said a Chinese naval vessel had informed a Japanese vessel that flight training would begin, but maintained that China had not provided specific information about the scale or location of the carrier-aircraft training. Japan also said its fighters had maintained safe distances and were conducting airspace-monitoring activities.
China Disputed Japan's Account
Beijing rejected Tokyo's characterization of the encounter. China's Foreign Ministry said its military training complied with international law and practice and argued that Japanese fighters had conducted close reconnaissance and interfered with Chinese exercises.
Chinese officials also said the use of search radar during carrier-based flight training was a normal safety measure. Japan disputed that explanation, arguing that fighter radars can serve both search and fire-control functions and that a pilot receiving the radar beam cannot necessarily determine its purpose.
The competing accounts are important: Japan described the radar exposure as dangerous, while China denied wrongdoing and accused Japan of creating the confrontation. Publicly available statements did not resolve the disagreement over the radar's intended function.
Washington Backed Tokyo's Concerns
The United States publicly supported Japan following the incident. A U.S. State Department spokesperson said China's actions were not conducive to regional peace and stability and reiterated that the U.S. commitment to Japan was unwavering, according to Reuters.
Japanese Defense Minister Shinjiro Koizumi later discussed the incident and the broader regional security situation with his U.S. counterpart. Japan's Defense Ministry said the two sides expressed serious concern about actions that could increase regional tensions and agreed to maintain close coordination.
China-Russia Bomber Patrol Added to Regional Pressure
The U.S.-Japan flight also followed coordinated Chinese and Russian military activity around Japan. Russian Tu-95 strategic bombers and Chinese H-6 bombers conducted a joint patrol in the region, prompting Japan and South Korea to monitor the aircraft.
Such patrols are part of a broader pattern of expanding China-Russia military cooperation. At the same time, operating near another country's air defense identification zone is not, by itself, equivalent to entering that country's sovereign airspace. An air defense identification zone, or ADIZ, is an area in which a state seeks advance identification of approaching aircraft; it extends beyond territorial airspace and does not confer sovereignty over international airspace.
Why the B-52's Role Matters
The B-52H is a long-range strategic bomber and one of the United States' most recognizable deterrence platforms. Its ability to carry both conventional and nuclear weapons gives deployments involving the aircraft strategic visibility, particularly when they occur during periods of heightened regional tension.
That capability, however, should not be confused with the payload carried on a particular mission. Public reporting on the December exercise did not establish that the bombers were carrying nuclear weapons. Describing the aircraft as nuclear-capable identifies a design and operational capability, not the armament used during this flight.
A More Integrated U.S.-Japan Alliance
The exercise illustrated the high degree of operational coordination developed between the U.S. and Japanese militaries. Japan hosts tens of thousands of U.S. military personnel, and the two countries regularly conduct air, maritime and ground exercises designed to improve interoperability.
Japan has also been expanding its defense capabilities amid concerns about North Korea's missile programs, China's growing military power and increased Chinese and Russian operations around the Japanese archipelago. These developments have made surveillance, air defense and rapid coordination with U.S. forces increasingly prominent parts of Japanese defense planning.
Taiwan and the Broader Strategic Context
The confrontation occurred against a wider deterioration in China-Japan relations, including disagreement over Taiwan. Beijing claims Taiwan as part of China and has not renounced the use of force to achieve unification. Taiwan is self-governed, and its future is a central security issue in the region.
Japanese officials have increasingly emphasized the importance of peace and stability across the Taiwan Strait, while China has strongly objected to Japanese statements that it views as interference in its internal affairs. Those disagreements provide important context for the December military encounters, but they do not establish that the radar incident or subsequent exercises were preparations for a specific conflict.
What the December Incidents Showed
The sequence of events demonstrated how quickly routine military monitoring, exercises and strategic patrols can become politically charged when several major military powers operate in close proximity. The December 6 radar encounter remained disputed, with Japan and China offering sharply different accounts of responsibility and the purpose of the radar use.
The subsequent U.S.-Japan B-52 exercise showed that Washington and Tokyo were prepared to make their alliance coordination highly visible. At the same time, the available evidence supports a narrower conclusion than some of the original rhetoric surrounding the episode: the flight was a military exercise conducted during heightened tensions, not an armed engagement, and the presence of nuclear-capable bombers did not establish that nuclear weapons were carried or contemplated for use.
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