New polls show surging support for U.S. air strikes against the Islamic State of Iraq and Syria, with widespread fears of the extremist group seemingly overwhelming the public's strong aversion to military conflicts after a decade of war.

A new Washington Post-ABC News poll finds 71 percent of Americans support air strikes against the Sunni insurgents in Iraq, up 17 percentage points from only three weeks ago and up 26 points from mid-June, when the public split evenly on the issue.

Republicans are by far the most supportive of military action, with 83 percent in the Post-ABC poll supporting air strikes in Iraq, up 22 points from mid-August. But support among Democrats and independents has also grown by double digits in recent weeks, and two-thirds of each group now backs air strikes against ISIS. Support for air strikes in Iraq crosses almost every demographic line except the youngest age cohort, where those under age 30 split 44 percent in support and 46 percent in opposition. Clear majorities of men and women, whites and non-whites, and liberals and conservatives support attacking the Islamic State.

So, what explains the public rapid rallying in support of another Iraq battle led by an unpopular President -- especially when 78 percent approved of withdrawing troops from the country in 2011?

Polls suggest the Islamic State's brutal tactics have hit Americans' terrorism nerve, with the group quickly gaining a reputation as threatening as al Qaeda. In the Post-ABC poll, nine in 10 adults see the Islamic State as a serious threat to U.S. interests, including 59 percent who call it a "very serious" threat. Even before the second of two Americans was reported to be executed, a Pew Research Center survey found 67 percent calling ISIS a "major threat" to U.S. well being, only four points shy of al Qaeda.

Public’s Views of Global Threats Facing the U.S.

Despite seeing ISIS as a major problem for the U.S.,  more than six in 10 respondents in the new CNN-ORC poll opposed sending U.S. ground troops to fight in Iraq and Syria. Obama has repeatedly dismissed such an option, though some lawmakers have voiced support for the idea and some American troops (mostly Special Forces) are already providing strategic guidance to the Iraqi military.

The massive gap in support for air strikes and ground troops speaks to the public's unwillingness to incur casualties or enter a prolonged military conflict, even in pursuit of fighting terrorism. The Islamic State's execution of American journalists appears to have shored up public support for taking action through less risky air strikes, but U.S. deaths could exert the opposite effect, as they did during the recently ended Iraq and Afghanistan wars.

Peyton M. Craighill contributed to this report