President Trump has named Army head Gen. Mark Milley as the next chairman of the Joint Chiefs of Staff. “I am pleased to announce my nomination of four-star General Mark Milley, Chief of Staff of the United States Army – as the Chairman of the Joint Chiefs of Staff, replacing General Joe Dunford, who will be retiring,” Trump tweeted Saturday morning. “I am thankful to both of these incredible men for their service to our Country! Date of transition to be determined.” The Joint Chiefs of Staff serve as the executive branch’s top military advisers. They work with the president, the secretary of defense and heads of other departments to coordinate and plan operations. Princeton-educated Milley, 60, has served four decades in the Army, including command positions in Iraq and Afghanistan. He has been Army chief of staff since 2015. Dunford is set to retire around next summer.