He said the strikes - from USA ships and Air Force bombers - destroyed three targets that were specifically associated with the Syrian regime's chemical weapons program.
Mattis said at the Pentagon that the air strike Friday used double the weapons of the one President Donald Trump ordered past year and were against targets the USA believed were "selective to hurt the chemical weapons program".
"The authoritarian Assad regime did not get the message a year ago as it was hit by American missiles after it carried out chemical weapons attack against its own people", Mattis said referring to the recent chemical weapon attack that killed 75 people last Saturday.
"We specifically identified these targets to mitigate the risk of Russian forces being involved", Dunford told reporters, adding the USA military advised Russia of airspace that would be used in the strike but did not "pre-notify them".
The defence secretary says Friday's strikes have "sent a clear message" to Assad and his "murderous lieutenants".
President Trump announced in a statement on Friday evening that the United States military would be conducting an immediate joint-military strike against Syria alongside the United Kingdom and France.
He also condemned the recent chemical attack by the Syrian state in the suburb of Douma.
The last target was a military command post and chemical weapons storage facility.
USA -led coalition strikes devastated targets across Syria Friday evening to ensure the Syrian regime understands the global community will not tolerate illegal use of chemical weapons.
Explosions are being heard to the east, west and south of Damascus as a result of the U.S., U.Okay. and France conduct airstrikes in retaliation for an alleged chemical assault by the Syrian authorities by itself people.
Trump in meetings with Mattis has pushed for an attack that would also hurt Russian Federation and Iran in addition to the Syrian government in response to an alleged chemical attack in Duma, the Wall Street Journal reported on Friday. He said the USA has "a lot of media and social media indicators that either chlorine or sarin were used".
Gen Dunford described the operation as a "one time shot" and said there had been no reports of any allied losses.
Following the strike, reports of a retaliatory actions emerged.
Syrian television reported that Syria's air defenses, which are substantial, have responded to the attack.
He said he became convinced Thursday, after he expressed those doubts. "But our efforts have been repeatedly thwarted" by Syria and Russian Federation, she said.
Dunford said the USA did not coordinate targets with or notify the Russian government of the strikes, beyond normal airspace "de-confliction" communications. A joint military operation, possibly with France rather than the USA in the lead, could send a message of worldwide unity about enforcing the prohibitions on chemical weapons.
"We confined it to the chemical weapons type targets".
"We were not out to expand this". French Defense Minister Florence Parly said that "with our allies, we ensured that the Russians were warned ahead of time". A US -led coalition has been conducting airstrikes in Syria since September 2014 as part of a largely successful effort to break the IS grip on both Syria and Iraq.
As our commander in chief, the president has the authority under Article II of the Constitution to use military force overseas to defend important USA national interests.
"On a strategic level, it's how do we keep this from escalating out of control, if you get my drift on that", he said. "So they did make adjustments". Trump wanted Mattis "to push the limits a little bit more", a White House official told the Wall Street Journal, while Mattis was said to be reluctant.
He added that Russian forces were not given advance notice, though the airspace over Syria was conflicted with Russian air forces, as per normal procedures. "We did not coordinate targets or any planning with the Russians".
The air strikes appeared to last about an hour. Mattis also reiterated that the sites of today's strikes were strategically chosen.
Ellsberg, who famously leaked thousands of documents almost half a century ago revealing that successive United States administrations had lied to the public about the Vietnam war, insisted that Defence Secretary Jim Mattis should be prepared to resist "impulsive and reckless" orders from Trump to go to war. "We believe it has sent a strong message to deter him from doing this again", he told reporters.