As Iraqi security forces took back the city of Ramadi late last year from the Islamic State, there was a near-constant presence overhead: The B-1B Lancer, the swept-wing bomber that dropped about a third of all coalition weapons on militants during its deployment from July through January. But the air war has reached a new phase. The B-1B has been redeployed to the United States, and the number of bombs falling on the Islamic State has plummeted since.

According to Air Force statistics, the United States dropped 2,694 bombs in January and 2,054 in February in Iraq and Syria. That’s down from 3,227 in November and 3,139 in December, which represented the height of an air war that began in August 2014. The 2,054 weapons released in February represented the lowest monthly total since last June, when 1,683 bombs were dropped, Air Force officials said.

The lull in the air campaign comes as the United States prepares to send the B-52 Stratofortress to the Middle East to supplement airstrikes. Air Force Secretary Deborah James said this month that infrastructure improvements have been made that will allow the B-52 to be deployed to theater. Sorties by the B-1B have been launched from Al Udeid Air Base in Qatar, where the United States maintains an operations center that oversees the air war. The B-52 is expected to arrive by April.

Other U.S. aircraft have continued to carry out airstrikes against the Islamic State, including jets flown by the Air Force, Navy and Marine Corps. Air Force officials said that combined, they would be able to handle the demand while the Pentagon’s larger bombers were not available. The Pentagon also deployed a company of Marines from the 26th Marine Expeditionary Unit last week to northern Iraq to establish a fire base from which 155mm Howitzer cannons can be launched and provide fire support to Kurdish troops nearby. That emerged over the weekend, after one of the Marines, Staff Sgt. Louis Cardin, 27, was killed by a 107mm rocket fired by the militants.

Over the last year, a higher volume of weapons dropped typically coincided with major ground operations. In July 2015, for example, the Air Force dropped 2,823 weapons across Iraq and Syria as Iraqi security forces launched an offensive against the Islamic State in Anbar province. The numbers spiked to their highest levels in the entire campaign in November and December, as offensives going on to take back Ramadi and the area around Syria’s Tishreen Dam.

The B-1B unit that just returned from the air war is the 37th Bomb Squadron, of Ellsworth Air Force Base in South Dakota. Using a handful of planes, it dropped more than 5,000 weapons between July and mid-January, said its commanding officer, Lt. Col. Joseph Sheffield. That represented about 30 percent of all weapons released by the Air Force in that time frame, and about half of all bombs in terms of bombs, he said.

The B-1B can carry 75,000 pounds of ordnance. Sheffield said that its ability to loiter above the battlefield for 10 to 14 hours at a time with a handful of refuelings allowed it to perform missions where it would drop at least 10 bombs in a single run.

“They could stay overhead and get a good feel for the battlefield, get a good situational awareness of where the ground force is moving, where is the enemy trying to strike from or where are they holed up or their hiding spots, and we would do multiple, multiple bomb runs,” he said.

About 90 percent of the strikes the B-1B squadron carried out were “dynamic,” meaning crews struck targets they observed based on actions on the ground, rather than relying on assignments provided before taking off.

“We did a lot of close-air support there in Ramadi, especially in the October through December time frame,” said one pilot, a captain who spoke on condition of anonymity due to security concerns. “We were pretty much there as a squadron a couple times a day, so it was unique… to see each day how the ground war was moving along and how the Iraqi security forces were moving along taking back the city.”