 -- The United States launched several airstrikes against ISIS targets inside Syria for the first time late Monday in what a defense official said was a "successful" start in a new front in the battle against the terror group and, separately, in potentially averting an imminent threat to the homeland from a shadowy al Qaeda group.

While the United States is still "assessing the effectiveness" of the bombing campaign against ISIS, which included up to 20 targets, the Pentagon believes “that we were successful in hitting what we were aiming at,” Pentagon Press Secretary Rear Adm. John Kirby said.

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"We took out command-and-control facilities, supply depots, some training areas, some vehicles and trucks, that kind of thing. Mainly, what we were going after was this group's ability to sustain itself, to resource itself and to, frankly, command and control and lead their forces,” Kirby told “Good Morning America,” referring to ISIS.

Many of the targets were in and around Raqqa, Syria, believed to be an ISIS stronghold, a defense official said Monday. Several Arab nations took part in the U.S.-led operation: Jordan, Saudi Arabia, Bahrain, Qatar and the United Arab Emirates, the U.S. military's Central Command said early today.

Separately, the U.S. military unilaterally launched eight strikes against the Khorasan Group, a little-known al Qaeda cell that Kirby said was “plotting and planning imminent attacks against Western targets to include the U.S. homeland.”

“It was on that basis that we struck targets, Khorasan targets, inside Syria. We believe the individuals [who] were plotting and planning it have been eliminated and we’re going to continue, as I said, to assess the effectiveness of our strikes going through today,” he said.

In a national address Sept. 10, President Obama said the first part of his strategy to counter ISIS was to "conduct a systematic campaign of airstrikes against these terrorists."

"Moreover, I have made it clear that we will hunt down terrorists who threaten our country, wherever they are. That means I will not hesitate to take action against ISIL [ISIS] in Syria as well as Iraq," Obama said. "This is a core principle of my presidency: If you threaten America, you will find no safe haven."

The stealth F-22 Raptor took part in the mission, a U.S. defense official said, marking the first time the pricey, controversial aircraft has been used in a combat operation.

In recent weeks, a self-described ISIS militant is believed to have killed two Americans on camera -- journalists James Foley and Steven Sotloff -- as well a British aid worker. The group is suspected of holding at least two more Americans and has publicly threatened a second Briton.

As of earlier today, the U.S. had launched nearly 200 strikes against ISIS in Iraq.

U.S. Ambassador to the United Nations Samantha Power Sunday told ABC News' "This Week" America would not conduct airstrikes in Syria alone. But already Secretary of State John Kerry claimed that some 40 countries, including a number of Arab nations, have offered various levels of support to the anti-ISIS effort. France announced last week it would join in airstrikes in the battle against ISIS.

ISIS, the Islamic State of Iraq and Syria, is the name taken in 2013 by what was originally an al Qaeda affiliate called al Qaeda in Iraq (AQI). In 2011, AQI moved into Syria, taking advantage of the country's civil war to gain power and recruits.

By 2013, ISIS leader Abu Bakr al-Baghdadi had spread his group's influence back into Iraq and changed the group's name to ISIS, "reflecting its greater regional ambitions," according to the State Department.

The group, which is no longer affiliated with al Qaeda after a public falling out earlier this year, is believed to have up to 30,000 members, including thousands of foreign recruits, hundreds of them Westerners. Using brutal tactics including the alleged mass execution of civilians and captured soldiers, the terror group has been able to control territory in Syria and cut a swath through Iraq.

ISIS, as the group has been identified by ABC News and other news organizations, refers to the Islamic State of Iraq and Syria. Different translations of the Arabic name al-Baghdadi gave his organization have spawned other English-language versions, such as the Islamic State of Iraq and al-Sham (also ISIS) or the Islamic State of Iraq and the Levant (ISIL).

ABC News' Jonathan Karl contributed to this report.