China has beefed up security on its border with North Korea by sending in thousands of army troops to work with the police and border guards already there. In addition to a growing number of North Korean refugees sneaking across, armed members of the North Korean army and border police have been coming across the Yalu river (often at night in small boats), robbing locals and then going back to North Korea. China has been aware of growing corruption in the North Korean army and police, but now it's reached the level where senior commanders either will not, or cannot, stop criminal activity by their subordinates.