The Japanese government following Seoul expressed protest over the violation of the airspace in the skies near the Takeshima (Dokdo) islands by Russia's A-50 early warning and control aircraft. However, the main thing here was a joint patrol mission of two Russian Tu-95MS and two Chinese H-6K strategic bombers along the Japanese territory. This was for the first time in the history of Russian-Chinese military ties that a joint patrol mission took place.
Firstly, it's clear that the joint flight proves that a new stage in bilateral military interaction has begun. Joint actions of Russian and Chinese combat and auxiliary aircraft to drill combat training and other tasks are coming to replace joint actions on land and sea.
This looks like the response of Russia and China to the growing military interaction between Japan, South Korea and the USA. Recent American plans to deploy missile defense elements in South Korea and Japan make Russia and China very much concerned. In particular, Russia views the deployment of Aegis Ashore in Japan as an element of the US global missile defense directed against Russia. Moreover, Russian military experts view Aegis Ashore as an offensive system that is potentially capable of being used for launching intermediate-range missile.
Apparently, such practice is likely to be nailed down in a future Russian-Chinese agreement on military cooperation.
Reconnaissance and intelligence seem to be the second aspect of the recent incident, and this is proved by the presence of the A-50 aircraft, which is used for the detection and tracking of airborne and seaborne targets, notifying command posts of the Armed Forces' automatic control systems of airborne and seaborne situation and for guiding fighter and attack aircraft on airborne, seaborne and ground targets. It is quite possible that in this case the bombers were to provoke air defense means, including radars, whereas the A-50 was to record their activities.
And it cannot be the other way.
Sometimes up to 800 flights to drill various combat training tasks, including the interception of aircraft of a potential enemy, dogfights, aerial reconnaissance, electronic intelligence, and combat patrol and military transportation missions, take place daily as part of joint American-South Korean exercises near South Korea.
New military facilities in South Korea, and more of them have been appearing recently within the framework of its cooperation with the USA, cannot fail to arouse justified interest of the armed forces of the neighboring countries. The USA, just as its regional allies, is involved in similar reconnaissance and intelligence activities.
Finally, the joint mission was flown in the South Korean air defense identification zone, which overlaps with similar zones of Japan and China. The USA and its allies don't recognize China's zone, China, just as Russia, doesn't recognize Japan's and South Korea's zones. Moreover, there is a dispute between Japan and South Korea over the territorial allegiance of the Takeshima archipelago. Finally, international law doesn't regulate air defense identification zones. Everyone flies into these zones defiantly ignoring them. These are the rules of the game of reconnoitering each other air defense systems.
From the point of view of international law, only the border of the territorial airspace 12 miles away from the coast matters. Actually, this is what both Japan and South Korea protest against. But the Defense Ministry of Russia told Seoul that aircraft of Russia's Aerospace Forces didn't breach the South Korean border during the routine flight.