Capability? China has the world’s largest military. They have the largest Naval fleet. China is and has been an expansionist power through its history. Their current aim is to restore Chinese pride and put China at its rightful place as the center of the universe. Any part they claim as theirs they are using those military assets to assert their claim, like the islands in Southeast Asian waters far away from their shores. This is the same attitude that allowed Russia to invade Ukraine twice.