China Marine Surveillance (CMS; Chinese: 中国海监; pinyin: Zhōngguó Hǎijiān) was a maritime surveillance agency of China. Patrol vessels from China Marine Surveillance are commonly deployed to locations in the South China Sea and East China Sea where China has territorial disputes over islands with its neighbors. The CMS has played a central role in China's increasing assertiveness in the South China Sea, encountering opposition from Japan, the Philippines and Vietnam in the disputed territories, as China tries to lock up natural resources to meet its demands as the world's largest energy consumer.