evidence: The inclusion of Heixiazi Island in China’s official maps last August caused a stir, yet Russia responded with restraint. The recent agreement to jointly develop Heixiazi Island while respecting national sovereignty reflects both nations’ willingness to set aside disputes under U.S. pressure. Putin’s support for local cooperation and the negotiation of Chinese ships’ access to the Tumen River is also a response to the ongoing Russia-Ukraine War and U.S. pressure. The trilateral cooperation among China, Russia, and North Korea in the Tumen River Delta region brings economic complementarity benefits, although some believe that this move may potentially undermine the security of the Sea of Japan in the future. With Russia preoccupied with the war in Ukraine, addressing eastern issues remains secondary, and the dispute with Japan over the Northern Territories is unlikely to escalate to armed conflict. Joint air and naval strategic patrols by China and Russia aimed at Japan are primarily a message to the U.S. rather than an immediate military threat. Thus, development in the Tumen River Delta will focus on economic rather than military aspects.