The start of US-led air strikes in Syria drew mixed reactions across the Middle East and around the world, ranging from staunch support from Britain to harsh condemnation by Russia, an old ally of the Assad regime.
In the Middle East, the fight against Islamic State militants is shifting regional dynamics, winning support from Arab nations that opposed previous US military inventions in the region. At least on the first day of bombing, there was little public backlash, with virtually no outcry beyond a pro-Islamic State protest in Istanbul.
Egypt, the most populous Arab country, is prepared to back the war against the militants, a foreign ministry spokesman said, noting the Egyptian government's fight against terrorists and political Islam.
Bahrain, Jordan, Saudi Arabia and the United Arab Emirates all issued statements acknowledging participation in the airstrikes, though none even mentioned the US involvement. Qatar, the other Arab partner in the airstrikes, said nothing, but earlier reports suggest it is not opposed to the strikes. (See: Obama warns of long haul as air strikes in Syria begin).
In Europe, one of the most straightforward voices of support came from Britain, which is not directly participating in the air campaign. "The prime minister supports the latest airstrikes against ISIL terrorists which have been carried out by the US and five other countries from the Gulf and Middle East," a Downing Street spokesman said.
In Syria, the reaction from Damascus was somewhat opaque. The Syrian foreign ministry simply noted that before the bombing started, Washington had notified Damascus through its envoy to the United Nations. US officials countered that they had provided only a general warning about the possibility of military action and had not coordinated with Bashr Al-Assad's government.
If Damascus was subdued, some of the Assad government's most prominent backers bluntly characterised the airstrikes as immoral and unlawful.
In Moscow, the foreign ministry called the airstrikes a violation of international law - and furthermore, it added, it was doomed to fail.
"Attempts to achieve one's own geopolitical goals in violation of the sovereignty of countries in the region only exacerbate tensions and further destabilise the situation," a Russian foreign ministry statement said.
More condemnation came from Lebanon, where Hezbollah is another ally of the Assad regime and has thousands of Shiite Lebanese militiamen fighting beside Syrian troops against the Sunni fighters of the Islamic State.
"Everyone knows that Hezbollah is against ISIS," said Hezbollah leader Hasan Nasrallah, using another acronym for the group. "We fight them and sacrifice and confront them."
But, he added, "America is not in a moral position that allows them to fight terrorism."
The US moved quickly to justify the aerial attacks as legal. The US ambassador to the United Nations, Samantha Power, told Secretary-General Ban Ki-moon in a letter that such attacks were permitted under a fundamental principle in the UN Charter that gives countries the right to defend themselves, including using force on another country's territory when that country is unwilling or unable to address it.
"The Syrian regime has shown that it cannot and will not confront these safe havens effectively itself," the letter states. "Accordingly, the United States has initiated necessary and proportionate military actions in Syria in order to eliminate the ongoing ISIL threat to Iraq, including by protecting Iraqi citizens from further attacks and by enabling Iraqi forces to regain control of Iraq's borders.