Satellite imagery shows what appear to be more than 500 personnel carriers and other military vehicles for China’s paramilitary People’s Armed Police hidden in a sports complex in the city of Shenzhen along the Hong Kong border. The display of military power, presumably as a threat that Beijing could intervene at any time to control Hong Kong demonstrators, comes as China refused entry to two U.S. warships requesting permission to dock in Hong Kong. The USS Green Bay, which is a transport dock, and the USS Lake Erie, a guided missile cruiser, had requested permission to dock in the financial hub in the coming weeks. Tensions between the U.S. and China have flared over trade talks and American criticism of Chinese-backed security forces’ clashes with pro-democracy protesters. China on Tuesday accused the U.S. of instigating protesters. Meanwhile, protesters occupying the Hong Kong International airport apologized after two days of clashes that shut down flight departures, as authorities deployed police and other security personnel to prevent demonstrators from returning to the travel hub.