The high-profile attacks — generally large bombs hitting markets, mosques or other "soft" targets that produce mass casualties — have dropped to about 70 in July from a high during the past year of about 130 in March, according to the Multi-National Force — Iraq.
"The enemy had the initiative and the momentum in '06," said Jack Keane, a retired general who is a chief architect of the increase in troop levels and mentor to Gen. David Petraeus, the top U.S. commander in Iraq. "We've got it now."
Keane spoke from Iraq.
Al-Qaeda militants generally attempt large, headline-grabbing incidents aimed at symbolic targets or mass casualties. Al-Qaeda in Iraq, for example, claimed responsibility for the April suicide bomb attack on parliament.
Successes against al-Qaeda have also been helped by shifting Sunni public opinion and a growing number of insurgent defections, the military says.
"Tribes and people are starting to stand up and fight back," said Brig. Gen. Mick Bednarek, deputy commander of the U.S. division north of Baghdad. "They are turning against al-Qaeda."
Some of the groups have provided intelligence on their former al-Qaeda allies, Lt. Col. Rick Welch, a staff officer who works with tribes, has said.
The increased security in many neighborhoods has also prompted more civilians to come forth with tips, officers said. The U.S. military gets 23,000 tips per month from Iraqis, four times more than last year, said Army Col. Ralph Baker, a former brigade commander in Iraq now assigned to the Pentagon.
Petraeus, who will give his assessment of the boost in troop levels in mid-September, said hundreds of al-Qaeda leaders have been killed or captured in the past month. He cautioned that al-Qaeda still has the "ability to carry out sensational attacks."
Al-Qaeda is generally behind the massive publicity-seeking attacks, but much of the sectarian violence and attacks on coalition forces is the work of Shiite militias, according to the U.S. military.
Violence from Shiite militias remains strong in some areas. In Baghdad, attacks from powerful armor-piercing roadside bombs, called explosively formed penetrators, or EFPs, increased to 35 in July from an average of 23 per month between March and June, said Maj. Steven Lamb, a spokesman for the U.S. division in Baghdad.
The U.S. military says the EFPs are supplied by Iran primarily to Shiite militias. Iran has denied the allegation.
Targeting militias has proved more sensitive than attacking al-Qaeda, since Iraq's Shiite-dominated government draws some of its support from Muqtada al-Sadr, the anti-American Shiite cleric whose followers form one of Iraq's largest militias.
In the past, the government of Prime Minister Nouri al-Maliki had sometimes blocked or criticized U.S. raids in Shiite strongholds. U.S. officers say that kind of interference has diminished. Petraeus said coalition and Iraqi forces have made inroads against Shiite extremist groups.