President Trump and his top national security aides huddled in the seclusion of Camp David on Friday, trying to formulate an effective new Afghanistan strategy after 16 frustrating years of war. The administration has struggled for months to fashion a plan for turning around the stalemated war. But stepping up the fight in a way that advances peace prospects may be even more difficult. Trump was meeting with Secretary of State Rex Tillerson, Defense Secretary Jim Mattis and other top military and diplomatic aides at the presidential retreat in nearby Maryland.