Army Gen. Mark Milley, chairman of the Joint Chiefs of Staff, and Gen. Valery Gerasimov, chief of the Russian General Staff, held a conversation that the Pentagon declined to further detail beyond acknowledging it had happened. “The military leaders discussed several security-related issues of concern and agreed to keep the lines of communication open,” the Pentagon said in a statement announcing the call. “In accordance with past practice, the specific details of their conversation will be kept private.”