During a speech at a meeting of the National Space Council, Mr. Trump announced plans to protect American interests in space through monitoring commercial traffic and debris, initiatives he said would be “great not only in terms of jobs and everything else, it’s great for the psyche of our country.”

Minutes later, the president zeroed in on Gen. Joseph F. Dunford Jr., the chairman of the Joint Chiefs of Staff, and tasked him with the undertaking of creating another branch of the military.