Trump's use of that last phrase harks back to President George W. Bush's premature declaration of victory in Iraq, where USA troops remain 15 years after the initial US military engagement there - a mistake some critics say they fear Trump might repeat on Syria.
The Pentagon says they believe the airstrikes "attacked the heart of the Syrian chemical weapons program" and "successfully hit every target".
May said while the strike was targeted at Syria, it sent a message to anyone who used chemical weapons.
Mr Mauro's warning comes after the U.S., the United Kingdom and France launched a series of missile strikes directed at the Syrian government forces. Last year's attack targeted the Shayrat air base outside Hama, which US officials said was used to launch a sarin gas attack that killed 70 people in the northern Syrian town of Khan Sheikhoun.
"An act of aggression against a sovereign state that is on the frontline in the fight against terrorism was committed without a mandate from the UN Security Council and in violation of the UN Charter and norms and principles of worldwide law", Putin said in a Kremlin statement.
The missiles targeted a scientific research facility that allegedly was connected to the production of chemical and biological weapons as well as two other units near Homs; a storage facility; and an important command post that the West also said served as a chemical-weapons equipment storage site.
"Dozens of men, women and children were massacred with chemical weapons", he said of the Douma incident a week ago - adding that "the red line had been crossed". Syrian state television claimed some of the missiles were shot down by the government's air defence systems.
Trump chastised Russian Federation and Iran for supporting "murderous dictators, " and noted that Putin had guaranteed a 2013 global agreement for Assad to get rid of all of his chemical weapons. "The attack this morning against Syria is a crime", Khamenei said.
British Prime Minister Theresa May, U.S. President Donald Trump and French President Emmanuel Macron were all on board with the strike.
German Chancellor Angela Merkel welcomed the move and said the strikes were a "necessary and appropriate military intervention".
Turkey, a North Atlantic Treaty Organisation member with forces in northern Syria fighting Kurdish militants, welcomed the strikes and described them as a proper action against the Assad regime. Still, he said that does little to dissuade Assad from resorting to barrel bombs and continuing to "slaughter" civilians, so long as he "doesn't violate global norms".
"Thank God this was less than we had feared". It is not about a regime change.
"When he sees these sorts of things, they outrage him", said a source familiar with the internal debate at the White House.
"Precise strikes on Syria ordered by Trump will complicate the situation in the Middle East", said Gu Zhenglong, researcher from Institute of International Studies in Xinhua News Agency. "We warned that such actions will not be left without consequences", said Anatoly Antonov, the ambassador to the United States, in a statement.
But it said skies were clear over Aleppo in the north, Hasakeh in the northeast, and Latakia and Tartus along the western coast, where key Syrian and Russian military installations are located.