Print WASHINGTON — The Justice Department this past week moved to drop cases that it brought last year against five visiting researchers accused of hiding their ties to China’s military, prompting questions about the department’s efforts to combat Chinese national security threats. The department filed motions Thursday and Friday to dismiss visa fraud and other charges it brought last summer against the researchers as the Biden administration grapples with holding Beijing accountable for its cyberattacks and its harsh crackdowns in Hong Kong and in the far western region of Xinjiang. The dismissals also come as the State Department’s No. 2 official, Wendy Sherman, is to meet in the coming days with Chinese officials in Tianjin.