NEW YORK – The United States is “proud to stand shoulder- to-shoulder” with Arab powers in bringing the fight against Islamic State to its territory in Syria, President Barack Obama said on Tuesday, after US air and naval forces carried out a major air assault on the terrorist network.The overnight attacks – the first of their kind on Syrian territory – incorporated the air forces of five nations, sea and surface-to-air assets, the participation of a sixth, Arab country and the tacit approval of another: Syria itself. The embattled government of Bashar Assad in Damascus did nothing to stop the strikes, and kept silent after the dust settled and the sun rose over the damage.Twelve hours after the attacks were over, Pentagon officials said that Syrian radar systems had been “passive” during the raids, which involved over four dozen planes.The US-led force struck targets of the extremist Sunni group in Dayr a-Zawr, Al-Hasakah, Abu Kamal and its headquarters in al-Raqqa city, alongside the air forces of Bahrain, Jordan, the United Arab Emirates and Saudi Arabia – all Sunni-dominated governments.Qatar participated in the attack as well, Obama said, thanking the government in Doha. The US Central Command’s forward headquarters is just outside the Qatari capital, and is America’s largest military base in the Middle East.At least 70 Islamic State fighters were killed in strikes that hit at least 50 targets in the provinces of Raqqa, Deir al-Zor and Hasakah, the Syrian Observatory for Human Rights said.In addition, at least 50 fighters and eight civilians were killed in strikes targeting al-Qaida’s Syrian affiliate, the Nusra Front, in northern Aleppo and Idlib provinces, it said. Most of the Nusra Front fighters killed were not Syrians, the Observatory said.In remarks from the South Lawn of the White House, Obama expressed “pride,” as well as gratitude to the countries involved in the attack. He praised their fight as a humane and common cause.“The strength of this coalition makes it clear to the world that this is not America’s fight alone ,” the US president said. “Above all, the people and governments in the Middle East are rejecting ISIL [Islamic State] and standing up for the peace and security that the people of the region and the world deserve.”Abu Dhabi, Amman, Riyadh and Manama all confirmed their participation within hours of the strike.Saudi Arabia participated “to support the moderate opposition, within an international coalition, to combat terrorism... and to support the fraternal Syrian people in returning security, unity and development to this devastated country,” a senior Saudi official said through the country’s state-run news agency.Obama, immediately after his remarks, left for New York, where he will speak at the United Nations General Assembly on Wednesday morning and then chair a special session of the Security Council on counterterrorism efforts.Clarifying initial reports that the US had formally notified the Assad government of the coming attack, State Department spokeswoman Jen Psaki said that a warning had been relayed, but nothing more.“We warned Syria not to engage US aircraft,” Psaki said.While Secretary of State John Kerry did not personally send notice to the Syrian regime, US Ambassador to the UN Samantha Power informed her Syrian counterpart and the UN secretary- general of the pending strikes. From the Red Sea and the northern Arabian Gulf, 47 Tomahawk missiles helped destroy or damage Islamic State targets throughout eastern Syria, including command and control infrastructure, a finance center, supply depots and its headquarters.Accompanying those missiles were US Air Force, Navy and Marine Corps units, including drones, bomber aircraft and fighter jets.Arab states contributed direct, kinetic power to the fight, in a rare show of force from the region alongside the American military. But the US was the only power outside the Middle East to participate.British Prime Minister David Cameron is expected to seek parliamentary approval to join the campaign this week, and plans to clarify his government’s role on Wednesday during his speech to the UN.Turkish President Recep Tayyip Erdogan vowed to contribute “necessary support” to the operation, be it “military or logistics.”Fighting in northern Syria in recent days has led to a flood of refugees spilling over Turkey’s southern border, estimated at more than 140,000 people.Russia and Iran remained silent in the hours after the attacks. In recent days, both governments have warned that strikes without the participation of the Assad government would constitute an “aggression” and a violation of international law.Hezbollah in Lebanon was the only group to condemn the attack on Tuesday, with its leadership putting out a televised speech opposing the US-led “military intervention.”Obama made the decision on Monday to begin air strikes against Islamic State in Syria, officials said, after already ordering nearly 200 strikes against Islamic State targets in Iraq since July.“It is not possible” to know the duration of the campaign, Obama wrote to Congress in a resolution on war powers, informing them of its progress.In a second war powers letter on Syria, Obama made no mention of Islamic State, but said that the targeting of Khorasan terrorists – once leaders in al-Qaida – was legally justified under congressional authorization passed in 2001.“I t must be clear to anyone who would plot against America and try to do Americans harm that we will not tolerate safe havens for terrorists who threaten our people ,” Obama said on Tuesday.Khorasan was about to enter the execution phase of a planned terrorist attack either in Europe or the US homeland, senior administration officials said. The US government only first acknowledged the existence of the Khorasan Group last week.Reuters contributed to this report.