Twitter post a day earlier that USA missiles "will be coming, nice and new and 'smart'". After the attack ceased and the early morning skies went dark once more, vehicles with loudspeakers roamed the streets of Damascus blaring nationalist songs.
It was not immediately clear whether Trump meant the allied military operation would extend beyond an initial nighttime round of missile strikes.
Russian Federation and Iran back Assad's regime in a complicated civil war that has raged for seven years.
Worldwide observers with the Organization for the Prohibition of Chemical Weapons have yet to reach the Damascus suburb of Douma, where the attack took place.
Dunford said there were many targets to choose from, but they chose ones that would minimize the risk to innocent civilians.
"The U.S. - the possessor of the biggest arsenal of chemical weapons - has no moral right to blame other countries", the Russian embassy in the U.S. said in a statement.
Despite foreign allies' expressions of confidence in the Syrian regime's culpability in the attack, United States officials have not ventured that far in public.
Medical sources and activists in Syria say following the alleged chemical attack last Saturday that blood, urine and hair follicle samples were smuggled in batches to Turkey during evacuations by the Syrian regime of rebel groups and their families. He said the USA has "a lot of media and social media indicators that either chlorine or sarin were used". He says a "combined operation" with France and the United Kingdom is underway.
"The United States has a vital interest to defend our interests and in specifically deterring the use and proliferation of chemical weapons", Mattis said in a news conference after the strikes were completed.
President Donald Trump is set to address the nation Friday night amid anticipation of a retaliatory strike for an apparent Syrian chemical weapon attack last week. "They can only say they found evidence or did not".
With strike fleets moving within range of Syria and the Russian military on alert to defend against a possible missile attack, tensions continue to run high.
On Wednesday, Trump tweeted that Russian Federation should get ready for new and "smart" missiles that would be coming to Syria.
US Secretary of Defense Jim Mattis (L) and Chairman of the Joint Chiefs of Staff General Joseph Dunford appear on Capitol Hill on Thursday.