In a muscular display of its rising military and economic might, China deployed a fleet of five warships on Friday near a gas field in the East China Sea, a potentially resource-rich area that is disputed by China and Japan. The ships, including a guided-missile destroyer, were spotted by a Japanese military patrol plane near the Chunxiao gas field, according to the Maritime Self-Defense Forces. It is believed to be the first time that Chinese warships have been seen in that area.