Obama's decision to send warplanes back to Iraq, three years after withdrawing the last US troops, marked a potential turning point in the two-month-old conflict.
After a first day of US air raids on fighters who had moved within striking distance of Kurdistan, a top official in the autonomous region said the time had come for a fightback.
Sailors launch F/A-18 fighter aircraft from the flight deck of the aircraft carrier USS George H.W. Bush (CVN 77) in the Gulf (Reuters Photo)
"Following the US strikes, the peshmerga will first regroup, second redeploy in areas they retreated from and third help the displaced return to their homes," Fuad Hussein told reporters Friday in the Kurdish capital Arbil.
Iraqi Foreign Minister Hoshyar Zebari, a Kurd who has boycotted cabinet meetings for weeks as relations soured with Baghdad, said that failing to arm the Kurdish peshmerga forces had been a costly mistake.
But he said the American air strikes had stopped the rot on the ground and allowed the federal and Kurdish authorities to unite behind the common cause of defeating the jihadists.
"The Iraqi army and the peshmerga are fighting side-by-side in the same trenches now," he said.
Iraq's military chief of staff, Babaker Zebari, told AFP on Friday that US advisers, peshmerga and federal top brass were "selecting targets" together.
The first US bombings struck IS positions and at least one convoy of vehicles carrying militants west of Arbil.
Obama said he had authorised the strikes in Iraq to protect US personnel serving there. "And, if necessary, that's what we will continue to do," he said Saturday.
A White House spokesman stressed Friday the strikes would be "very limited in scope", but Babaker Zebari said he thought US air support would extend to other areas.
He said the intervention would allow joint action to reclaim large tracts of land lost to the Sunni extremists since they launched their devastating offensive on June 9, exactly two months ago.
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'One or two days'
Obama also justified the US intervention on Thursday with the risk of genocide against the small Yazidi minority, many of whose members have been trapped on the Sinjar mountain for a week.
"The United States can't just look away. That's not who we are. We're Americans. We act. We lead. And that's what we're going to do on that mountain," he said Saturday.
US cargo planes have been dropping food aid on the barren mountain, but Yazidi MP Vian Dakhil, whose poignant appeal in parliament this week made her the public voice of her community, said time was running out.
"We have one or two days left to help these people. After that they will start dying en masse," she told AFP.
The Yazidis, who worship a figure associated with the devil by many Muslims, are a small and closed community, one of Iraq's most vulnerable minorities.
Among the hundreds of thousands of people who fled their homes in northern Iraq were several other minorities such as the Shabak, Assyrian Christians and Turkmen Shiites.
Smoke rises after airstrikes by the U.S. forces targeting Islamic State militants near the Khazer checkpoint outside of the city of Irbil in northern Iraq. (AP Photo)
UNESCO chief Irina Bokova called it an "emerging cultural cleansing".
"The US should strike Sinjar, even if there are civilian casualties. It's better than letting everyone die," Dakhil said.
The lack of food and water coupled with searing temperatures drew some of them down from the mountain but the walk to Syria or Turkey is long and dangerous.
The International Rescue Committee (IRC) is providing emergency care to around 4,000 people who crossed safely into northeastern Syria.
"They suffer from dehydration, sunstroke and some of them are seriously traumatised," the IRC's Suzanna Tkalec told AFP, adding that many had walked all day for several days.
Impact of strikes
On Thursday alone, up to 100,000 Iraqi Christians fled their homes in the Nineveh plains, west of the main jihadist hub of Mosul.
Chaldean Catholic leaders said the largest Christian town in the country, Qaraqosh, had been emptied of its inhabitants in a matter of hours.
While it remains unclear how much longer and deeper into Iraq US warplanes will strike, analysts said the intervention had the potential to turn the tide on jihadist expansion.
"The air strikes could certainly soften up some of the IS positions and make it easier for counter-offensives on the ground by the Kurdish peshmerga," John Drake of the AKE Group security company said.
He also said surgical strikes could take out some control centres and disrupt the Islamic State's chain of command.
The latest IS gains saw militants take over Mosul dam, the country's largest, vast swathes of land both east and west of their Iraq headquarters and further abolish the border with the Syrian half of the "caliphate" it proclaimed in late June.
A propaganda video released by the group on Saturday showed its fighters carrying their black flag and taking down government signs at sites they recently conquered.
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