Errant Bombing of Syrian Troops Weakens U.S. Effort to Curb Violence

Instead, the mistaken bombing -- American pilots thought they were aiming at Islamic State jihadists but instead killed more than 60 Syrian soldiers, according to the Russian military -- again exposed the White House's struggle to put together a coherent strategy in a multisided war. The United States has conflicting aims in the war, from defeating the Islamic State to ultimately easing Mr. Assad out of office.

Nearly a year after Mr. Kerry began a diplomatic process to reduce the violence, and then a political accord for a transition in power, he appears no closer to that goal than when he started. The early American calls for Mr. Assad to leave office have been muted because of fears that a power vacuum in Damascus would be exploited by jihadists.

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The situation in Syria on Sunday showed that the cease-fire that began last Monday was fraying. Fighter jets fired at least four missiles at opposition neighborhoods in Aleppo, Syria's largest city, while Syrian government helicopters dropped improvised barrel bombs on a village in the country's south, killing at least nine people, a conflict monitor said.

Many American officials believe that the Russians were never serious about the deal that was sealed in Geneva. The officials argue that the Russians were looking for an excuse that would derail it and keep a status quo in which they have more control over events in Syria than any other power, with the possible exception of Iran. If so, the accidental bombing made that process easier.

... the deadly bombing underscored how difficult it has been to ensure that the American and Russian militaries do not become entangled on Syria's complicated battlefield, much less to coordinate their targeting.

... Sunday's airstrikes in Aleppo, which is divided between government and opposition forces, were the first to hit the city since the agreement went into effect last Monday. It was unclear whether the strikes had been launched by Syrian or Russian jets, both of which frequently bomb the opposition.