An AH-64 Apache helicopter patrols the skies over eastern Afghanistan on Sept. 16. The helicopters are now believed to be flying combat missions in Iraq against the Islamic State, providing close-air support in what is effectively another expansion of the U.S. role there. (Photo by Master Sgt. Kap Kim/U.S. Army)

The United States has expanded its air war against the Islamic State, hitting the militant group for the first time with airstrikes launched from U.S. helicopters. Doing so will likely improve the Pentagon’s ability to help Iraqi forces on the ground, especially against mobile targets — but it also greatly increases the risks Americans will face.

The first American helicopter strikes against the militants were announced Sunday. Officials with U.S. Central Command, which oversees military operations in the Middle East, said that U.S. troops had launched three airstrikes in Syria and six in Iraq. Four of the strikes in Iraq occurred northeast of the western city of Fallujah, while one occurred southeast of Hit and another was carried out northeast of Sinjar.

U.S. officials announced Monday that three more airstrikes had been carried out in both Iraq and Syria, and that the operations in Iraq included “rotary wing” aircraft along with fighter jets and bombers that have been involved in the campaign for weeks. The helicopters were flown by the U.S. Army, said Maj. Curtis Kellogg, a spokesman for U.S. Central Command.

U.S. military officials declined to specify the kind of helicopters used, but they are likely AH-64 Apaches operated by the U.S. Army out of Baghdad International Airport. They carry a variety of weapons, including Hellfire missiles and 30mm cannons. Pentagon officials said early in July that some would be sent to Iraq as the United States expanded the scope of its military mission there, but had not previously disclosed their involvement in any airstrikes.

The use of helicopters will help hit mobile targets like armed trucks or ground troops, said Chris Harmer, a retired Navy helicopter pilot who is now an analyst with the Institute for the Study of War. Fighter jets and bombers are effective hitting fixed targets, but their pilots will struggle against moving targets without someone on the ground who can provide targeting information, he said.

“The more lively the fight is, the more likely you are to need rotary wing aircraft to assist forces on the ground,” Harmer said.

Using Apaches introduces considerably more risk to the U.S. troops involved, however. While fighter jets and bombers might have to contend with mechanical malfunctions, they can operate in Iraq unimpeded by rocket-propelled grenades and other weapons that can be used to target low-flying aircraft. Helicopters have been shot down over Iraq, Afghanistan, Somalia in the last 25 years.

The Islamic State is believed to have confiscated powerful surface-to-air missiles known as MANPADS from the Syrian military after capturing an airfield there in August. While both RPGs and MANPADS — short for Man Portable Air Defense Systems — have been used to down American helicopters, many MANPADS are designed to home in on the heat from an aircraft’s engine, making them more accurate than common RPGs, which are unguided.