Days of intense bombing that could soon put the critical city of Aleppo back into the hands of Syrian President Assad’s forces. The USA says there could be no military solution to Syria. 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.

The Russian military action has changed the shape of a conflict that had effectively been stalemated for years. Suddenly, Mr. Assad and his allies have momentum, and the United States-backed rebels are on the run. If a cease-fire is negotiated here, it will probably come at a moment when Mr. Assad holds more territory, and more sway, than since the outbreak of the uprisings in 2011.

Mr. Kerry enters the negotiations with very little leverage: The Russians have cut off many of the pathways the C.I.A. has been using for a not-very-secret effort to arm rebel groups, according to several current and former officials. Mr. Kerry’s supporters inside the administration say he has been increasingly frustrated by the low level of American military activity, which he views as essential to bolstering his negotiation effort. READ MORE