Obama authorized "targeted airstrikes" if needed to protect U.S. personnel from fighters with the Islamic State, formerly known as the Islamic State in Iraq and Syria, or ISIS. The U.S. military also could use airstrikes to prevent what officials warn could be a genocide of minority groups by the Islamic State fighters.
U.S. warplanes patrolling the skies over northern Iraq have a "green light" to go after perceived ISIS threats to the Kurdish capital, Irbil, or to minority populations, said deputy national security adviser Ben Rhodes.
The first strike involved 500-pound laser-guided bombs on a "mobile artillery piece" used by ISIS at about 6:45 a.m. ET Friday, Pentagon spokesman Rear Adm. John Kirby said.
It came in response to an Islamic State advance this week on what officials call U.S. interests in Iraq's Kurdish region in the north. The militants took towns from the Kurdish fighting force known as the Peshmerga.
Before the onslaught, the region had been the most stable in Iraq and a cooperative ally of the United States. U.S. military advisers and consular personnel are stationed in Irbil.
The mobile artillery battery hit Friday was based outside Irbil, Kirby said.
In announcing his decision Thursday night, Obama said the militants would get hit "should they move towards the city."
Kurdish leaders have been pleading for the United States or NATO to buttress their forces against the Islamic State from the air. The President seems to have heard their appeal.
"We do whatever is necessary to protect our people," Obama said, adding, "We support our allies when they're in danger."
U.S. airstrikes also could hit the Islamic State if militants continue to endanger the lives of thousands of ethnic Yazidis stranded in mountains by the militants' siege. Obama and other administration officials are using the term "genocide" when referring to the threat to the internal refugees.
Last weekend, ISIS militants raided the Yazidi town of Sinjar in northern Iraq. Yazidis, one of Iraq's smallest minorities, are of Kurdish descent and their religion is considered a pre-Islamic sect that draws from Christianity, Judaism and Zoroastrianism.
The Islamic State has executed people who don't share their fanatical interpretation of Sunni Islam and posted videos of their killings to the Internet.
"Convert to Islam or die" is the militants' ultimatum to those captured.
They also have beheaded victims and placed their heads on spikes to strike terror in the population, a senior administration official said.
Before Obama spoke Thursday night, two U.S. military cargo planes airdropped 5,300 gallons of water and 8,000 meals onto Mount Sinjar, where some Yazidi children had died from dehydration.