For months now the United States has insisted there can be no military solution to the Syrian civil war, only a political accord between President Bashar al-Assad and the fractured, divided opposition groups that have been trying to topple him. But after days of intense bombing that could soon put the critical city of Aleppo back into the hands of Mr. Assad’s forces, the Russians may be proving the United States wrong. There may be a military solution, one senior American official conceded Wednesday, “just not our solution,” but that of President Vladimir V. Putin of Russia . That is what Secretary of State John Kerry faces as he enters a critical negotiation over a cease-fire and the creation of a “humanitarian corridor” to relieve starving […]