The Islamic State has slashed fighters’ salaries in Raqqa, the group’s de facto headquarters in Syria, by up to 50 percent, American intelligence analysts say.

The United States and its allies still drop most of their bombs — nine out of every 10 — on Islamic State fighters, weapons or other targets that pop up on the battlefield. The goal is not only to punish the Islamic State, but also to help Iraqi troops, who announced a push toward Falluja this week, and friendly Syrian militias.

The biggest shift in the past year, however, has been in the remaining 10 percent of targets: mostly fixed sites behind the front lines that specialists are taking much more time to analyze. General Brown insisted on increasing the quality of these so-called deliberate targets, which include headquarters, barracks and storage facilities, to ensure that the strikes would have a deeper strategic effect on the Islamic State.

The military caught its first big break last May, when it seized information about the leadership structure and financial operations of the Islamic State, also known as ISIS or ISIL. The information was gathered during a Delta Force commando raid in eastern Syria in which Abu Sayyaf, a leader of the terrorist group, was killed and his wife, Umm Sayyaf, was captured.

In the past year, the United States has increased the number of spy planes and other surveillance aircraft over Iraq and Syria, as well as the number of targeting specialists assigned to the mission. Hundreds more Special Operations forces are now on the ground in the two countries, sending back valuable information, as are thousands of Iraqi troops and Syrian militia members whom the Americans and their allies are training and advising.

“We do have a much better sense now for what this enemy looks like, how this enemy operates and how they’re structured,” said Col. Steve Warren, the military’s chief spokesman in Baghdad.