WASHINGTON — President Obama signed a secret order in recent weeks authorizing a more expansive mission for the military in Afghanistan in 2015 than originally planned, a move that ensures American troops will have a direct role in fighting in the war-ravaged country for at least another year. Mr. Obama’s order allows American forces to carry out missions against the Taliban and other militant groups threatening American troops or the Afghan government, a broader mission than the president described to the public earlier this year, according to several administration, military and congressional officials with knowledge of the decision.
