Japan’s Air Force Steps Up Its Scrambles. What Are the Risks?


Editor’s Note: A version of this article was originally published by The Interpreter, which is published by the Lowy Institute, an independent, nonpartisan think tank based in Sydney. War on the Rocks is proud to be publishing select articles from The Interpreter.

By international standards, the Japan Air Self-Defense Force is very busy. It scrambles fighters daily to intercept multiple aircraft penetrating Japan’s Air Defense Identification Zone (ADIZ) – the bloc of airspace established over, and usually somewhat beyond, a nation’s territory in which any unknown approaching aircraft is sought to be identified. If determined hostile, the aircraft are then turned away or in extremis engaged.

The number of JASDF scrambles to identify unknown ADIZ-penetrating aircraft have steadily risen from about 300 annually in 2012 to a peak of almost 1200 in 2016. In 2017, the number of scrambles declined to around 900: Fifty-five percent against Chinese intruders and 43 percent Russian. A broadly similar ratio held up to end of the third quarter of 2018 when there were 758 scrambles, an average of almost three a day. Most Chinese aircraft intercepted are fighters; for Russia, intelligence collector aircraft are the most frequently encountered.

The JASDF’s fleet of some 215 F-15J aircraft bears the brunt of scramble tasking. The F-15J is well suited for such air policing tasks, having a fast cruise speed to reach intruding aircraft quickly, a good range and endurance, and reasonable maneuverability for close-in visual identification of air targets.

Since 2016, Japan’s air force has often launched four aircraft for each scramble. The front two aircraft undertake visual identification, while the two rear aircraft manage any additional intruders that join in and try to interfere. Scrambles now may also use E-2C airborne early warning and control aircraft to coordinate the intercept, sanitize the airspace and avoid tactical surprise. The JASDF is taking its daily scrambles very seriously.

These daily scrambles are gradually wearing the F-15J fleet out. The concern is that China has some six times more fighters than the JASDF and could further ramp up intrusions whenever it considers appropriate. The in-service life of Japan’s F-15J fleet is now almost a decision that lies with China. The easiest solution seems reducing the number of scrambles undertaken but that would be a major strategic shift.

Japan considers China is engaging in a salami-slicing strategy of incremental power projection to gain de facto control of the Senkaku Islands, just as it successfully did in the South China Sea. China’s 2013 ADIZ declaration over the islands appears part of this strategy. If Japan cuts back on intercepting intruding Chinese aircraft, it will create a vacuum that China will fill.

Moreover, if China’s air activities go unchallenged, other countries may gradually come to accept or at least acquiesce to China’s claims over Japan’s. This worry drives Japan to believe it needs to continuously demonstrate its determination to maintain the sovereignty of its territory. For Japan, a tangible response to every Chinese intrusion is essential.

In contrast, Russia’s intrusions seem related to the U.S. alliance, not to Japan’s territorial integrity. In the north it may be possible to adopt a reduced air defense posture of “strategic silence” that would only periodically intercept Russian ADIZ intruders. This would make Japan’s air defense activities strategically unpredictable while sustaining deterrence and cutting scramble numbers by up to half.



Regardless, the F-15J force is steadily aging making replacement an important issue. In mid-December, the Japanese government surprised many in announcing 105 F-35A/B aircraft would be acquired to replace the older, un-upgraded half of the F-15J fleet. It is noteworthy that the new aircraft buy is in addition to the 42 F-35As Japan ordered earlier to replace F-4EJ aircraft.

Japan feels under intense U.S. political pressure to negotiate a bilateral trade deal that reduces the American tradable goods deficit. The highly visible purchase of a large number of F-35 aircraft will help reduce this deficit and perhaps relax U.S. pressure.

The F-35 purchase’s usefulness for this political purpose is being maximized by also agreeing to buy U.S. not Japanese-assembled aircraft and by being included with a buy of nine E-2D airborne early warning and contro aircraft, also being assembled in the United States. Japan is, however, slipping in a small quid pro quo. Some of the finance for the 105 F-35A/B buy depends on the United States helping Japan sell its old F-15J aircraft to other air forces, presumed to be in the East Asian region.

There are also some operational issues. Unlike the F-15, the F-35 was designed to be a strike aircraft. Accordingly, the F-35’s airframe in the air policing role lacks endurance, has limited maneuverability for close in visual identification tasks and is rather costly to operate at the rate the JASDF is currently flying its F-15Js.

Moreover, flying the F-35 daily against Chinese and Russian aircraft risks compromising its technical characteristics. Inevitably, both China and Russia will collect signals and signature intelligence on any intercepting F-35s.

Surprisingly, the 42 F-35B Short-Take-Off-Vertical-Landing aircraft may be the most useful variant for the peacetime air-policing role. The closest F-15J base to the Senkaku Islands is Naha, 400 km away, but Shimoji Island’s small airfield that could be configured for F-35B air policing operations is only 200 km distant. Flying missions from Shimoji would halve the time to intercept Chinese aircraft operating around the Senkakus.

These are busy times for the JASDF’s fighter force. It is one to watch in this new era of great power competition.



Dr. Peter Layton is a Visiting Fellow at the Griffith Asia Institute, Griffith University. A retired RAAF Group Captain, Peter has extensive experience in force structure development and taught national security strategy at the US National Defense University.  He has written extensively on defense and security matters, and was awarded the US Exceptional Public Service medal for force structure planning work. In 2006, he won the RUSI Trench Gascoigne Essay Prize for original writing on contemporary issues of defense and international security. He is the author of the book Grand Strategy.


Image: Japan Air Self-Defense Force photo