HONG KONG • As Hong Kong police clashed with protesters on July 28, firing tear gas and rubber bullets into a crowd in the central business district, Chief Executive Carrie Lam was at a very different event across the city. She was guest of honour at a youth summer camp organised by China's People's Liberation Army (PLA).

Her host was Major-General Chen Daoxiang, a senior Chinese officer in Hong Kong who used another public event on Wednesday - the celebration of the 92nd anniversary of the creation of the PLA - to deliver a clear message: The world's largest army was prepared to put down the protest movement in the city should China's President Xi Jinping give the order.