BRUSSELS (AP) — A seven-month investigation by the Associated Press and the Oxford Internet Institute, a department at Oxford University, found that China’s rise on Twitter has been powered by an army of fake accounts that have retweeted Chinese diplomats and state media tens of thousands of times. The accounts covertly amplified propaganda that can reach hundreds of millions of people — often without disclosing the fact that the content is government-sponsored. The move onto Western social media comes as China wages a war for influence — both at home and abroad — on the internet, which President Xi Jinping has called “the main battlefield” for public opinion. Twitter and Facebook are blocked inside China.