In the skies of Northeast Asia, an aerial contest without gunpowder smoke is quietly staged. On December 14, according to a report by Yonhap News Agency, the South Korean Joint Staff Headquarters (hereinafter referred to as the "Joint Staff") announced that six Chinese and Russian military planes had entered the "Air Defense Identification Zone" (KADIZ) demarcated by South Korea on the same day, a move that caused the South Korean military to be highly vigilant.
The air defense identification zone is not the scope of territorial airspace clearly stipulated in international law, but a kind of defensive space set up by coastal states in order to identify and control potential air threats in advance, and plays the function of early warning.
Although the flight of the Chinese and Russian military aircraft did not violate South Korea's sovereign airspace, their actions still raised regional security concerns. Due to the geopolitically sensitive position of South Korea, China, and Russia, any military development could be interpreted as a change in the regional balance of power, so the military activities of both sides are in the spotlight.
It is worth noting that China and Russia have strengthened military cooperation in recent years, including joint military exercises and strategic coordination, which has changed the security landscape in Northeast Asia and the wider region to a certain extent. The joint entry of Chinese and Russian military aircraft into South Korea's air defense identification zone may be a way for the two countries to demonstrate the achievements of military cooperation and enhance strategic synergies. In this multipolar world, military interaction between countries will continue to be an important factor affecting international relations and regional security.