Smoke rises above a damaged building following a U.S.-led coalition airstrike against ISIS positions during clashes between Iraqi security forces.

The U.S.-led air campaign against ISIS militants in Syria, which ground to a near halt in late October, has intensified in recent days.

Coalition forces carried out 56 strikes against ISIS in Syria in the eight days from Oct. 30 to Nov. 6 after going the previous eight days with only three strikes, according to U.S. military figures. The strikes have focused on the towns of Mar’a, al Hawl, al Hasakah and Dayr az Zawr.

The United States and its allies carried out a dozen strikes in Syria on Saturday, the U.S. military said in a statement on Sunday.

The jump in air and rocket strikes in Syria coincided with Washington’s shift in approach to the conflict after efforts to train Syrian rebels to fight ISIS collapsed. Russia also deployed warplanes to Syria, adding pressure on Washington to take more effective action.

The White House confirmed on Oct. 30 it would deploy dozens of special operations forces to Syria to advise and assist a coalition of rebels already on the ground. Defense Secretary Ash Carter also signaled his intent to intensify the air campaign.

U.S.-backed forces in Syria have renewed their drive to capture the eastern town of al Hawl and to push ISIS away from the Turkish border along the Mar’a line north of Aleppo.

The U.S. air campaign has been criticized by Republican lawmakers and others who say the intensity of the strikes is insufficient to reverse the advances of ISIS fighters, who overran large parts of Iraq and Syria last year.

The air campaign reached a peak in July, when warplanes carried out 887 air strikes – 518 in Iraq and 369 in Syria, U.S. military data analyzed by Reuters shows.

Since then, strikes in Iraq have remained in the range of 500 per month, while in Syria they dropped steadily each month, reaching a low of 117 in October, daily strike tallies show.

U.S. military officials downplay the significance of the strike data, saying they represent the ebb and flow of battle and are affected by things like bad weather, which may prompt changes in targeting on a particular day.

“We are not focused on numbers of strikes. We are focused on effects of our strikes,” Army Colonel Steve Warren, a U.S. military spokesman in Baghdad, said in an email.

Coalition strikes since July in Syria have been concentrated around al Hasakah, a town near the northeastern frontier on the route to Sinjar, Tal Afar and Mosul in northwestern Iraq. About 37 percent of U.S. air strikes in Syria focused on that town.

More than 11 percent of U.S. air strikes have hit the area around Raqqah, the ISIS’s Syria headquarters, and more than 10 percent have targeted the militants around Kobani, a city near the Turkish border ISIS tried to capture.

U.S. bombing in Iraq has targeted Ramadi, Sinjar and Mosul. Eighteen percent of U.S. strikes hit ISIS militants near Ramadi, while 14 percent hit the group in the Sinjar area and 13 percent targeted it near Mosul.

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