QUAD unnerves China, U.S F-22 Raptors team up with Australian F-35 fighters

Defence outposts on artificial islands; China claims almost all of South China Sea. South China Sea is a key gateway for a large chunk of the world's merchant shipping. The sea contains rich fishing grounds & reportedly; reserves of undiscovered oil, gas. Hence, South China Sea is a key economic & strategic sub-section of the Indo-Pacific.