WASHINGTON — After years of resisting the pull of more Mideast conflicts, President Barack Obama has sent the military back into action in Iraq, where he once accused his predecessor of waging a ‘‘dumb war.’’
U.S. planes on Friday bombed Islamic militants who were towing artillery outside Irbil near U.S. personnel, the Pentagon said.
The aggressive insurgency threatens to undermine Obama’s legacy as the commander in chief who ended a long and unpopular war in which nearly 4,500 American troops died.
It also raises fresh questions about whether Obama’s desire to end the war clouded his assessment of the risks of fully withdrawing U.S. troops, as well as his judgment about the threat posed by the extremists.
Obama insisted the U.S. was not moving toward a protracted conflict.
‘‘I will not allow the United States to be dragged into fighting another war in Iraq,’’ he said late Thursday at the White House.
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He also said the U.S. had completed airdrops of humanitarian aid to Iraqi religious minorities who are under siege.
The moves are, so far, more limited in scope than the invasion undertaken by President George W. Bush after the Sept. 11 attacks.
The chief rationale for Obama’s authorization for military strikes in Iraq was to protect American forces serving in Irbil. They include some of the forces the president sent in this summer to help train and assist Iraq’s struggling security forces.
In trying to help Iraq protect civilians, Obama said the U.S. has a responsibility to stop imminent massacres. It’s an echo of the argument he used when the U.S. joined NATO’s bombing campaign in Libya in 2010.
Obama has not followed the same path in Syria’s civil war, where more than 170,000 people have died.
The conditions that returned the U.S. to military action in Iraq can be traced back months — or years, as the president’s critics contend.
As recently as January, Obama was dismissive of the Al Qaeda breakaway Islamic militants. In an interview with the New Yorker magazine, he said comparing the group to the terrorist network established by Osama bin Laden was like comparing a junior varsity basketball team to an NBA squad.
Yet U.S. intelligence and defense officials were warning about the potential threat from the Islamic State, which had strengthened in Syria.
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Obama’s comments reflected his limited appetite for wading back into Iraq or starting a military engagement in Syria, where he authorized an air assault last summer but never gave the order to go ahead.
Obama’s critics draw a direct connection between that approach and his decision to withdraw all American troops from Iraq in late 2011. He did so in large part because Iraq’s government refused to sign a security agreement providing U.S. troops immunity.
But White House opponents say the president should have pushed harder for a deal in order to avoid the type of situation now unfolding.
‘‘We are already paying a very heavy price for our inaction, and if we do not change course, the costs of our inaction will only grow,’’ said Sens. John McCain, R-Ariz., and Lindsey Graham, R-S.C.
They called on Obama to extend his authorization of airstrikes against the Islamic State beyond Iraq and into Syria.
The flurry of action comes as Obama’s approval ratings have plummeted, and the public’s opinion of his foreign policy moves is lagging.
He has faced questions about his ability to influence world events, from Russia’s provocations in Ukraine to the fighting between Israel and Hamas.
Obama long has been skeptical about the effectiveness of military action, and he made clear that U.S. airpower would not solve Iraq’s problems.
‘‘There’s no American military solution to the larger crisis in Iraq,’’ he said.