US war planes joined the air forces of Bahrain, Jordan, Saudi Arabia, UAE, and Qatar to hit dozens of ISIS targets inside of Syria. The US also hit the al-Qaeda affiliate fighting against Bashar Assad in Syria, the Al-Nusra Front, and their close ally, Khorasan, thus intervening directly in the civil war on behalf of Syrian government forces.

The president made no mention of hitting other terrorist groups in his statement about attacking ISIS in Syria. Indeed, hitting the Nusra Front is beyond the scope of "degrading and destroying" ISIS.

The explanation given was that Nusra presented an imminent threat to US interests.

Reuters:

Targets included "fighters, training compounds, headquarters and command and control facilities, storage facilities, a finance center, supply trucks and armed vehicles," it said.

Separately, U.S. forces acting alone launched strikes in another area of Syria against an al Qaeda-linked group, the Nusra Front, to "disrupt imminent attack" against U.S. and Western interests by "seasoned al Qaeda veterans", CentCom said.

The Syrian Observatory for Human Rights, which monitors the war in Syria, said at least 20 Islamic State fighters were killed in strikes that hit at least 50 targets in Raqqa and Deir al-Zor provinces in Syria's east.

It said strikes targeting the Nusra Front in the northern provinces of Aleppo and Idlib had killed at least 50 fighters and eight civilians. The Nusra Front is al Qaeda's official Syrian wing and Islamic State's rival. The Observatory said most of the fighters killed there were not Syrians.

The air attacks fulfill President Barack Obama's pledge to strike in Syria against Islamic State, a Sunni Muslim group that has seized swathes of Syria and Iraq, imposing a mediaeval interpretation of Islam, slaughtering prisoners and ordering Shi'ites and non-Muslims to convert or die.

Islamic State vowed revenge.

"These attacks will be answered," an Islamic State fighter told Reuters by Skype from Syria, blaming the "sons of Saloul" - a derogatory term for Saudi Arabia's ruling family - for allowing the strikes to take place.

President Obama goes before the UN today where it is expected he will call for a world wide coalition to defeat ISIS. It would be a more credible appeal if the president had the backing of Congress before he went into Syria. But Congress didn't want to vote on such a controversial issue so close to the election, and Obama was of no mind to ask them anyway.

The Syrian government was informed of the strikes before they occurred:

The Syrian government said Washington had informed it hours before the strikes. Secretary of State John Kerry had sent a letter to Damascus through his Iraqi counterpart, it said.

A ministry statement read on state television said Syria would continue to attack Islamic State. It was ready to cooperate with any international effort to fight terrorism and was coordinating with the government of Iraq.

The United States has previously said it would not coordinate with Assad's government. Washington says Assad must leave power, particularly after he was accused of using chemical weapons against his own people last year.

Islamic State's Sunni fighters, now equipped with U.S. weapons seized during their advance in Iraq, are among the most powerful opponents of Assad, a member of a Shi'ite-derived sect. They are also battling against rival Sunni groups in Syria, against the Shi'ite-led government of Iraq and against Kurdish forces on both sides of the border.

In recent days they have captured villages from Kurds near Syria's Turkish border, sending nearly 140,000 refugees across the frontier since last week. The United Nations said it was bracing for up to 400,000 people to flee.

Washington is determined to defeat the fighters without helping Assad, a policy that requires deft diplomacy in a war in which nearly all the region's countries have a stake.

Whether intentional or not, the perception is unmistakable; the US has become Assad's air force and his most effective weapon against ISIS and other Islamist groups.

Obama waited until Congress was out of town to strike. That might sit well with most members - including those of his own party - who insist the president needs congressional authorization to expand the war.

As long as the vote comes after the election.