Photo by Karim Sahib/AFP/Getty Images 
 
 This post has been updated with the latest developments in Iraq. 
 
 President Obama has authorized U.S. airstrikes against the Sunni militant group ISIS in northern Iraq. If you’re just catching up on the story now, here’s a quick FAQ. 
 
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 What’s been going on with ISIS for the last few weeks? 
 
 While the world’s attention has been mainly focused on the war in Gaza, the deteriorating situation in eastern Ukraine, and the Ebola outbreak in West Africa, ISIS’s campaign of terror in both Syria and Iraq has continued. In Syria, fighting between ISIS and Bashar al-Assad’s forces has led to some of the bloodiest days of the conflict so far. 
 
 Joshua Keating Joshua Keating is a staff writer at Slate focusing on international affairs and author of the forthcoming book, Invisible Countries. 
 
 In Iraq, things seemed to have reached a stalemate, with ISIS’s rapid advance through the country stopped short of Baghdad and the predominantly Shiite areas of southern Iraq. All the same, more than 1,700 Iraqis were killed in July, making it one of the deadliest months since the height of the Iraq war. 
 
 Then, earlier this week, ISIS captured three towns in northern Iraq from Kurdish forces and now appears to have taken control of the country’s largest dam. It marks the first defeat of the Kurdish Peshmerga forces, and there are reports that the Kurdish capital, Erbil, is now threatened. 
 
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 Members of the small Yazidi ethnic group in northern Iraq have perhaps fared the worst. Having been driven from their towns, between 10,000 and 40,000 predominantly Yazidi civilians are now stranded on a barren mountain with few supplies. They are facing an extraordinarily grim choice, between death by dehydration if they stay where they are or being slaughtered by ISIS if they flee. 
 
 Who are the Yazidis? 
 
 There are about 600,000 Yazidis worldwide, mostly in Iraq, Iran, Turkey, and Syria. Though often considered an offshoot of the Kurds, they consider themselves a distinct ethnic group. They follow a unique religion that blends elements of Sufi Islam and Zoroastrianism. Like Shiites, Christians, and a number of other groups in Iraq, ISIS considers them apostates and has killed at least 500 Yazidis thus far. 
 
 Why is the U.S. intervening only now? 
 
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 While the U.S. sent 300 military advisers to Iraq last month, the Obama administration has been wary of direct military intervention on behalf of the Iraqi government, making such aid contingent upon the formation of a more inclusive government that gives greater political representation to Sunnis and Kurds, and preferably one without Prime Minister Nouri al-Maliki in charge. 
 
 But Maliki has shown no willingness to form such a government, and in the meantime the lay of the land in Iraq has worsened. The situation facing the Yazidis has been called a potential genocide, with President Obama himself using the G-word Thursday night. The taking of the Mosul Dam could portend catastrophic consequences. And Kurdistan’s Peshmerga forces, thus far considered the only fighting force in Iraq capable of rolling back ISIS, have now been dealt a string of major defeats. Meanwhile, ISIS fighters are reportedly getting dangerously close to Baghdad. 
 
 In short, things got much worse, much more quickly than anticipated. 
 
 What will a U.S. intervention entail? 
 
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 So far, the U.S. says it has bombed ISIS artillery positions outside of Erbil that were threatening Kurdish defenses. 
 
 There doesn’t seem to be much reason to doubt the president, though, when he says that “American combat troops will not be returning to fight in Iraq." This administration has shown little enthusiasm for intervention in either Iraq or Syria and will likely try to keep this mission as limited as possible. 
 
 Of course, all interventions are subject to mission creep, and a limited campaign of airstrikes to “prevent a potential act of genocide,” as the president put it, could easily turn into a longer air campaign on behalf of the Iraqi government against ISIS, a somewhat awkward proposition given Iran’s role as Baghdad’s primary patron. 
 
 While it’s seems unlikely that a significant number of American boots will be back on Iraqi soil anytime soon, one of the Obama administration’s signature achievements—ending the long U.S. military engagement in Iraq—looks a lot more tenuous than it did a few months ago. 
 
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 How does this end? 
 
 While essentially every government in the Middle East is united in its opposition to ISIS, nobody seems able to stop it. (In addition to its gains in Iraq, the group recently made its first major foray into Lebanon.) So far, it has worked to the group’s advantage that many of the governments it is fighting—Syria, Iraq, the United States, Iran, Kurdistan—are also at odds with each other. Whenever the group faces a setback on one front, it seems to melt back into the wilderness and launch a new campaign somewhere else. 
 
 Ironically, ISIS’s campaign against the Kurds may end up helping unify the Iraqi state. Until last week, it looked like the destabilization caused by ISIS’s rampage through the country would aid the cause of Kurdistan, which has been pushing for full independence from Iraq for years and had been feuding with Maliki’s government over oil revenues. Now, Maliki is ordering his air force to help the Kurds. Iraq’s various factions, as well as Baghdad’s odd-couple patrons, Iran and the United States, may be forced to work together to confront the most serious threat the country has faced since the worst days of the Iraq war. ||||| Story highlights U.S. makes another drop of food and water to Iraqis stranded on mountain 
 
 Fighter jets and drones targeted an ISIS mortar position and a convoy, Pentagon says 
 
 The warplanes targeted an ISIS convoy near Irbil, the Pentagon says 
 
 ISIS militants capture dam north of Mosul, Kurdish official says 
 
 U.S. fighter jets and drones repeatedly bombed Sunni Islamic extremists in northern Iraq on Friday, targeting what officials described as ISIS artillery units and convoys advancing on the Kurdish regional capital of Irbil. 
 
 The airstrikes ramped up America's involvement in Iraq where ISIS, which calls itself the Islamic State, is seizing control of towns and key infrastructure in an advance that has forced hundreds of thousands to run for their lives. 
 
 The critical Mosul Dam is now in the hands of ISIS fighters, authorities said, while 150 hundred miles to the east tens of thousands of Iraq's minority Yazidis were trapped on a mountain by ISIS fighters below who vowed to kill them. 
 
 News of the second round of U.S. airstrikes came just after the governor of Irbil told CNN that ISIS may be as close as 30 kilometers (just over 18 miles) from the city of more than a million people. 
 
 The airstrikes began just hours after President Barack Obama authorized "targeted airstrikes," saying in a televised address late Thursday that the United States had an obligation to protect its personnel in Iraq and prevent a potential genocide of minority groups by ISIS. 
 
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 Obama said there will be no buildup of U.S. combat troops in Iraq. "As commander in chief, I will not allow the United States to be dragged into fighting another war in Iraq," the President said. 
 
 Hitting ISIS 
 
 Two U.S. F/A 18 fighters first struck an ISIS artillery unit outside of Irbil, dropping two 500-pound laser-guided bombs at about 6:45 a.m. ET Friday, Pentagon spokesman Navy Rear Adm. John Kirby said. 
 
 Later, a drone targeted an ISIS mortar position, Kirby said. When ISIS fighters returned to the site a short time later, the drone struck the target again, he said. 
 
 That was followed a short time later by a second round of airstrikes, carried out by four U.S. fighter jets, that targeted an ISIS convoy of seven vehicles and another mortar position, Kirby said. 
 
 The F/A 18s made two passes, dropping a total of eight laser-guided bombs, he said. 
 
 Before the ISIS 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. 
 
 At this point, the United States has hundreds of military personnel in Iraq, including advisers sent in recent weeks to coordinate with Iraqi and Kurdish military officials in response to the ISIS rampage. The USS George H.W. Bush and other Navy ships also are in the region, and the FA/18s in Friday's initial strike came from the aircraft carrier, officials said. 
 
 Airstrikes are "very important" because ISIS fighters are well-armed and are outgunning the Kurdish forces, thanks to the weapons the militants seized from the Iraqi military in Mosul, Irbil Gov. Nawzad Hadi said. 
 
 Even as the airstrikes were under way, there was news that ISIS militants captured Iraq's largest hydroelectric dam, just north of Mosul, Iraq's second-largest city. According to a senior Kurdish official, the militant fighters have been using U.S.-made weapons seized during fighting from the Iraqi army, including M1 Abrams tanks. 
 
 There had been conflicting reports about who controlled the dam on the Tigris River, with heavy fighting under way between ISIS fighters and Kurdish forces, known as peshmerga. U.S. officials have warned that a failure of the dam would be catastrophic, resulting in flooding all the way to Baghdad. 
 
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 In other fighting, an Iraqi airstrike killed 45 ISIS fighters and injured 60 Friday in the northern town of Sinjar, the country's state-run National Media Center said. 
 
 Sinjar is the town that ISIS overran last weekend, forcing tens of thousands of Yazidis to flee into surrounding mountains without food, water or shelter and prompting concerns of a potential genocide. The Yazidis are of Kurdish descent, and their religion is considered a pre-Islamic sect that draws from Christianity, Judaism and Zoroastrianism. 
 
 U.S. flights prohibited 
 
 In other signs of a growing regional conflict: The Federal Aviation Administration issued a notice prohibiting U.S. airlines from flying through Iraqi airspace "due to the hazardous situation created by the armed conflict." 
 
 The developments showed that the lightning advance by ISIS fighters across northern Iraq this year has become a battle for the nation's future and overall stability in a part of the world wracked for decades by periodic war. 
 
 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. 
 
 Airstrikes are also possible to help Kurdish forces end the siege by ISIS in the northern Iraqi mountains, where tens of thousands of Yazidis have sought refuge, Earnest, the White House spokesman, said Friday. 
 
 ISIS fighters have surrounded the Yazidis on the ground below. 
 
 "If there can be American military might that can tip (the) balance, we'll look for an opportunity to do that," Earnest said. 
 
 Kurdish pleas 
 
 In announcing his airstrike 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 ISIS 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." 
 
 Before Obama announced the airstrikes, 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. 
 
 U.S. F/A-18 E/F Super Hornet 
 
 Photos: U.S. military's fighter fleet Photos: U.S. military's fighter fleet An F/A-18E Super Hornet from the Sunliners of Strike Fighter Squadron 81 taxis onto a catapult before launching from the flight deck of the aircraft carrier USS Carl Vinson. Hide Caption 1 of 9 Photos: U.S. military's fighter fleet An F-15E Strike Eagle was designed for long-range, high-speed interdiction without relying on escort or electronic warfare aircraft. It was derived from the F-15 Eagle, which was developed to enhance U.S. air superiority during the Vietnam War. Hide Caption 2 of 9 Photos: U.S. military's fighter fleet A F-22 Raptor flies over Marietta, Georgia, home of the Lockheed Martin plant where it was built. The F-22 is the only fighter capable of simultaneously conducting air-to-air and air-to-ground combat missions. Hide Caption 3 of 9 Photos: U.S. military's fighter fleet F-16 Fighting Falcons are parked at the Aerospace Maintenance and Regeneration Center in Tucson, Arizona, on December 11, 2004. General Dynamics (which was later sold to Lockheed) delivered the U.S. Air Force its first F-16As in 1979. More than 4,500 of the fighters have been built, and they are used by more than 20 nations in addition to the United States. Hide Caption 4 of 9 Photos: U.S. military's fighter fleet A F-35C conducts a test flight over the Chesapeake Bay on February 11, 2011. Inspections of F-35 engines have been ordered after a runway fire at Eglin Air Force Base on June 23. The F-35 Lightning II has been beset by delays and cost overruns in the years since its introduction. Hide Caption 5 of 9 Photos: U.S. military's fighter fleet An A-10 Thunderbolt II from the 52nd Fighter Wing, 81st Fighter Squadron, Spangdahlem Air Base, Germany, in flight during a NATO Operation Allied Force combat mission. Hide Caption 6 of 9 Photos: U.S. military's fighter fleet An F/A-18 Hornet is pictured aboard the USS George H.W. Bush on May 19, 2009. The F/A-18 Hornet, a late-'70s contemporary of the Air Force's F-16 Fighting Falcon, became the workhorse of U.S. carrier-based air power and still supplements the Navy's and Marines' more current fleet of F/A-18E and F/A-18F Super Hornets. It is designed as both a fighter and an attack aircraft. Hide Caption 7 of 9 Photos: U.S. military's fighter fleet Pilots perform daily flight checks on their F-5E/F Tiger aircraft in Key West, Florida, on January 7, 2005. The Vietnam-era aircraft -- one of several offshoots of the original Northrup F-5s that went into service in the early 1960s -- is used to simulate adversary aircraft in training. Hide Caption 8 of 9 Photos: U.S. military's fighter fleet A AV-8B Harrier lands on board the USS Nassau on April 14, 1999, after a strike mission into Kosovo. The AV-8B Harrier is a single-engine ground-attack aircraft capable of vertical or short takeoff and landing. Though production of the aircraft ceased in 2003, the U.S. Marine Corps is looking at systems enhancements and plans to continue using Harriers well into the next decade. Hide Caption 9 of 9 
 
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 According to a U.S. official, a Predator drone flying overhead indicates the Yazidis have 63 of the 72 pallets dropped with aid supplies. It's not clear if the other pallets missed the drop zone or are in ISIS hands. 
 
 Late Friday, the Defense Department announced that U.S. military planes made another airdrop of food and water for Iraqi citizens stranded on Mount Sinjar. 
 
 The British government said Friday it would support the U.S. humanitarian effort and planned airdrops of its own. 
 
 French President François Hollande joined the growing chorus of condemnation of the ISIS attacks and called on the international community to respond. 
 
 "France is ready to take its part," Hollande said in a statement from his office that called for the European Union "to take an active role very quickly" and put in place all the necessary assistance to respond to the crisis. 
 
 Meanwhile, the United Nations in Iraq was "urgently preparing a humanitarian corridor to allow those in need to flee the areas under threat," said Nickolay Mladenov, the special representative to the U.N. secretary-general. 
 
 He welcomed the "cooperation between the Government of Iraq, the Kurdistan Regional Government (KRG) and the international community to help prevent genocide and fight terrorism," according to a U.N. statement. 
 
 Iraqi Foreign MInister Hoshyar Zebari told reporters Friday from Irbil that his government is working with the KRG -- including supplying the Kurdish peshmerga with ammunition and military helicopters. 
 
 This hasn't always been the case "because of political issues," the KRG's official website notes. Yet the same site reported that Zebari said "it is now clear that the peshmerga and the Iraqi security forces are fighting together against a common enemy." 
 
 Beheadings 
 
 ISIS 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. 
 
 Already, the Obama administration is rapidly funneling weapons to Iraqi forces. Factories are operating seven days a week to produce them, a senior administration official said. 
 
 The administration has pushed for Iraqi Prime Minister Nuri al-Maliki's Shiite-dominated regime to be replaced by an ethnically more inclusive government 
 
 But two Republican senators said in a statement that the President's actions do not go far enough. And the United States should not wait on Iraq to pull together before Washington takes action. 
 
 Sens. John McCain of Arizona and Lindsey Graham of South Carolina want to see U.S. forces take the fight to ISIS. 
 
 "It should include U.S. airstrikes against ISIS leaders, forces, and positions both in Iraq and Syria," their statement read. ||||| In a statement made Thursday night, President Obama said he has authorized military strikes on Islamic State militants if they continue their advancement on the city of Irbil, where military personnel and the U.S. consulate are located. (AP) 
 
 President Obama said Thursday night that he has authorized two new, major actions by the U.S. military in Iraq: airstrikes against militants with the Islamic State if U.S. interests or personnel are threatened, and humanitarian assistance for thousands of civilians who have fled the Islamist advance in northwest Iraq and are now trapped on a mountain. 
 
 Even those two specific missions are more complicated than that, however. 
 
 First, the U.S. humanitarian mission on Mount Sinjar began Thursday with airdrops by military aircraft, but it could require targeted airstrikes in order to “break the siege” at the base of the mountain and allow authorities to provide more assistance to the civilians, Obama said. They would be conducted in coordination with the Iraqi government and Iraqi Kurdish security forces known as pesh merga. 
 
 Second, the advance of the Islamic State near Irbil appears to be a line in the sand for the Obama administration. The United States has both diplomats and military advisers in the city, which is the capital of the Kurdistan region of Iraq. The United States also has a consulate in Irbil, creating enough interests that the United States wants to protect the city from harm. 
 
 “To stop the advance on Irbil, I’ve directed our military to take targeted strikes against [Islamic State] terrorist convoys should they move toward the city,” Obama said. “We intend to stay vigilant, and take action if these terrorist forces threaten our personnel or facilities anywhere in Iraq, including our consulate in Irbil and our embassy in Baghdad.” 
 
 
 
 In this image released by The White House, President Obama meets with the National Security Council in the Situation Room of the White House on Thursday in Washington. (AP Photo/The White House, Pete Souza) 
 
 Here’s what we know now about the specifics of these missions: 
 
 Humanitarian air drops 
 
 The U.S. military launched one C-17 and two C-130 cargo planes near Mount Sinjar on Thursday, dropping 8,000 prepackaged meals and 5,300 gallons of water, senior U.S. officials said. The aircraft were accompanied by two F/A-18 fighter jets, which came out of an undisclosed air base in the Middle East. The Pentagon did not indicate which units or branch of service operated any of the aircraft. 
 
 Pentagon officials said in a statement that the three cargo planes released a total of 72 bundles of supplies. They flew over the drop area for less than 15 minutes, and left the area before Obama announced the actions in his 9:30 p.m. address. 
 
 Senior U.S. officials left open the possibility that the United States could conduct more airdrops in coming days if it’s needed. That appears possible, considering human rights workers have estimated that up to 40,000 civilians may be trapped on the mountain, unable to return their homes for fear of being killed by militants. 
 
 “We feel that this is a unique and urgent humanitarian challenge,” one senior officials said Thursday night. 
 
 
 
 This image made from video taken on Sunday shows Iraqis people from the Yazidi community arriving in Irbil in northern Iraq after Islamic militants attacked the towns of Sinjar and Zunmar. Around 40,000 people crossed the bridge of Shela in Fishkhabur into the northern Kurdish region of Iraq after being given an ultimatum by Islamic militants to either convert to Islam, pay a security tax, leave their homes, or die. (AP Photo via AP video) 
 
 Preparing for airstrikes 
 
 The advance of militants across northern Iraq has been watched closely this week, but a new wave of attacks threatened Irbil in a way it had not been before, U.S. officials said. That led the president to authorize airstrikes if necessary. 
 
 U.S. officials also said that with the increased threat now facing Irbil, the United States has either surveillance drones or manned aircraft flying over the area almost constantly, keeping tabs on militant movements. 
 
 Defense Secretary Chuck Hagel said in a statement Thursday night that U.S. military advisers in Iraq will continue to assess ways to help train and assist Iraqi forces, and will provide undisclosed “increased support” once Iraq has formed a new government. Most of the troops there are U.S. Army Special Forces. 
 
 Outgoing Iraqi Prime Minister Nouri al-Malikihas faced fierce criticism for appointing friends to key positions, allowing corruption and cutting Iraq’s Sunni population out of the political process, fueling the insurgency. A new prime minister could be selected in coming days, U.S. officials signaled Thursday night. 
 
 UPDATED, Friday, Aug. 8, 9 a.m.: U.S. airstrikes in Iraq have begun after militants launched artillery rounds at Kurdish troops defending Irbil. Rear Adm. John Kirby, the Pentagon press secretary, posted this tweet:
– President Obama gave the green light last night for the US military to launch airstrikes in Iraq, but why now? Some explanations: Twofold mission: The US has already dropped food and supplies to Iraqis trapped on Mount Sinjar by extremist fighters from the Islamic State, or ISIS, and it may drop more. As for the airstrikes, targeted ones may be necessary near the mountain to "break the siege" there, says Obama, and allow more help to arrive and avert a "genocide." The bigger reason for the possible airstrikes, however, seems to be to halt the advance of the extremist fighters in the north. 'Line in the sand': Though the US did not intervene as the Islamic State swept across much of Iraq in recent weeks, the city of Irbil in northern Iraq "appears to be a line in the sand," writes Dan Lamothe in the Washington Post. It's the Kurdish capital, and the US has diplomats and military advisers stationed there among the American allies. (The Islamic State also reportedly controls the country's largest dam, in the northern city of Mosul.) How far? "The question arises: How far is Mr. Obama willing to go?" writes Peter Baker in the New York Times. Obama said "there is 'no American military solution' to the Iraqi insurgency, pointing again to the need for a new politically inclusive government in Baghdad. What he might do if that fails he did not say. And while aides stressed this is a narrow mission, they acknowledged scenarios in which it could expand." Reversal: "The return to military engagement in Iraq is a reversal for Mr. Obama, whose early opposition to the war that toppled Saddam Hussein, and his promise to end it, fueled his long-shot campaign for the White House," write Carol E. Lee and Felicia Schwartz at the Wall Street Journal. "It also puts a spotlight on what has become a familiar feature of the Obama presidency, in which the leader of the most powerful military in the world has become defined by his reluctance to use it." Unity after all? "Ironically, ISIS's campaign against the Kurds may end up helping unify the Iraqi state," writes Joshua Keating at Slate. The Kurds have long been at odds with Nouri al-Maliki's government, but now he's ordering his air force to help them. "Iraq’s various factions, as well as Baghdad’s odd-couple patrons, Iran and the United States, may be forced to work together to confront the most serious threat the country has faced since the worst days of the Iraq war." Full text: Read the president's statement here.