Russia revealed that during the last three months of 2015 it had flown (using about 100 warplanes and attack helicopters) over 4,300 sorties against Islamic terrorist rebels in Syria. Russia believes its air strikes are much more effective than those flown by Western and Arab air forces because Russia has better intelligence. In addition to intel from over 200,000 Syrian soldiers and pro-government militiamen, Russia also obtained target information from 150 rebel groups (over 5,000 rebels) willing to cooperate against ISIL (Islamic State in Iraq and the Levant).
Russian air strikes have killed over 2,500 people so far, about a third of the victims have been civilians. This is condemned as a war crime by many but is also a less publicized (especially by the Russians) reason why the Russian air strikes have been so much more effective than the larger number of American ones. Russia does not abort a strike because there is too much risk of civilian casualties. This makes ISIL more vulnerable to air attack than when just the Americans were handling it. The U.S. believes that only a few percent of the people its air strikes kills are civilians. The ROE (Rules of Engagement) Russia uses against ground targets ignores the use of human shields or the presence of a lot of civilians for whatever reason.