With no set timescale for military engagement and few certainties in Baghdad's political crisis, US President Barack Obama's week-old Iraq intervention threatens to monopolize the rest of his presidency.
Two-and-a-half years after he oversaw the withdrawal of US troops from Iraq, Obama has ordered airstrikes against a jihadist group but has vowed that America will not be drawn into ground combat.
But he has also said, in pledging his support to political transition in Baghdad, that Washington was ready to help Kurdish troops and the as yet un-formed new Iraqi government "battle these terrorists."
"President Obama seems to have adopted a strategy of making a long-term military commitment to Iraq," wrote Anthony Cordesman, of the Center for Strategic and International Studies, who suggested it might be the "best option" or the "least bad and filled with risks."
Some of Obama's Republican rivals have denounced the approach, judging it imperative to hit harder and faster against the rapid advance of the Sunni jihadists from the so-called Islamic State.
Hawkish senators John McCain and Lindsey Graham argue the US should go beyond humanitarian intervention and should pursue IS fighters without waiting for a political transition in the Iraqi capital, .
The White House says it has two goals: protect US personnel stationed in Arbil, the capital of Iraq's autonomous Kurdish region, and avert a possible genocide on Mount Sinjar, where refugees from the Yazidi religious minority are sheltering from IS attacks.
On Wednesday, a group of around 20 US soldiers deployed to the mountain on a reconnaissance mission and concluded that there was no need for a large-scale US intervention beyond dropping aid and advising the Kurdish forces battling to break the siege.
But, even assuming the Yazidis to escape, the defense of Arbil will continue and it appears unlikely Washington could accept IS control of large swathes of territory, leaving Iraq's government to its fate.
- The day after -
And if the US operation continues, the military's targets would be expected to evolve.
"So far, mostly what we have been doing is very limited scale strikes against a handful of very vulnerable exposed targets," said Stephen Biddle of the Council on Foreign Relations, citing Pentagon reports of strikes on trucks and armored vehicles parked on roads.
But public perception of the US engagement could profoundly change if a US airstrike hits "a school, or a hospital," he warned.
Obama has stressed there is "no American military solution" in Iraq, insisting "The only lasting solution is for Iraqis to come together and form an inclusive government."
The US president hasn't hidden his regrets over the aftermath to the NATO airstrikes in Libya in 2011, which helped local rebels overthrow long-time dictator Moamer Kadhafi.
While he argues military action was justified, he has lamented the absence of parallel political efforts. Libya is now once again in chaos, with rival militias fighting for control of the capital.
The US ambassador and three more Americans were killed on September 11, 2012 in an attack on a diplomatic compound in the Libyan city of Benghazi, a worrying omen for a president with one eye on the US consulate in Arbil.
"So that's a lesson I now apply every time I ask the question, 'Should we intervene militarily? Do we have an answer (for) the day after?" Obama explained in a recent interview with the New York Times.
"Our military is so capable, that if we put everything we have into it, we can keep a lid on a problem for a time," he added.
"But for a society to function long term, the people themselves have to make decisions about how they are going to live together."
This reflection explains the reasoning behind Washington's decision to throw all its weight behind the new prime minister-designate, Haidar al-Abadi, in the hopes he will form a more inclusive government and avoid the marginalization of the Sunni minority, which has led some local groups top support the jihadist offensive.
But even if Nuri al-Maliki -- who has defied growing international pressure to step aside as prime minister -- gives in, building a new, more balanced government would be difficult.
"I don't think we are going to solve this problem in weeks," Obama has warned. "I think this is going to take some time."
Biddle suggested the battle could last years, at least until Obama bows out in January 2017: "It's very likely that the air strikes he started last week are probably still going on when leaves office."