A day of intense terror attacks by Hamas that killed more than 200 Israelis united observers in shock—not just at the toll, but at the sophistication of the assaults. 

Saturday’s attack was “unprecedented and an apparent quantum leap in Hamas’s capabilities,” said Steven A. Cook, a senior fellow for Middle East and Africa Studies at the Council on Foreign Relations.

Mark Hertling, a former commander of U.S. Army Forces Europe, tweeted, “Operation ‘Al Aqsa Storm’ isn’t the typical Hamas attack. Israel is facing attacks on multiple domains & fronts, from an opponent with allies & supporters (Hezbollah, Islamic Jihad, Iran, even Russia), during a symbolic time (50th anniversary of Yom Kippur). Much more complex.”

The surprise attack, which was apparently unforeseen by Israeli intelligence, began in the early morning hours of a Jewish holiday. Hamas forces fired multiple rockets into Israel, broke through barriers with explosives, made beach assaults with speedboats, and dispatched troops on pickup trucks, motorcycles, and even paragliders to infiltrate towns in southern Israel.

AP reporters on the ground described the situation as horrific. 

A senior White House official, speaking not for attribution, said many Israeli civilians were killed and others, including children, had been taken hostage.

The Biden administration is focused on supporting Israel and making sure that violence “does not spread to the West Bank,” the official told reporters. “We want to try to make sure this is contained in Gaza.” 

While the White House refused to speculate on what lay ahead, CFR’s Cook said Israel would likely respond in similarly unprecedented fashion. “Expect a very significant Israeli military operation. I don’t see how they respond with a ground incursion. The old rules of air strikes and artillery barrages no longer apply. This means a lot of bloodshed in the coming days and weeks.”

Indeed, by evening, the Israeli response had begun with airstrikes on Gazan cities, the New York Times reported. And Israel had begun calling up reservists for a campaign dubbed Operation Iron Swords, according to the online magazine The Judean.

Cook said Hamas had clearly been planning the weekend attack for some time—and may have had help from Iran. 

“Given its sophistication, operational security, and lethality, one has to wonder whether the Iranians had a role in helping them,” he said. “We know that the IRGC Qods Force commanders met with Hamas leaders in the spring along with Islamic Jihad, and Hizballah. The Supreme Leader was has been quite active threatening the Israelis on social media.”

The senior administration official said the White House did not have any direct intelligence to say that Iran was linked to the attack. 

“We’re going to be looking at that very closely,” he said. 

UN peacekeeping forces in Lebanon were reportedly told to return to bases in anticipation of a possible Hezbollah attack. Hamas leader Ismail Haniyeh reportedly vowed to escalate the fight to the West Bank, while Israeli Prime Minister Benjamin Netanyahu promised to “turn all Hamas hiding places into rubble” and even urged Palestinians to leave Gaza (without saying where they should go).

The senior administration official wouldn’t speculate about Israel’s expected response. He did say that the commander of U.S. Central Command, Gen. Eric Kurilla, was talking to his counterpart in the Israeli military. 

This was “just regular coordination about some of the needs that Israel anticipates,” the spokesman said. “We will continue to provide Israel with support during this critical time including close, deep intelligence sharing.” 

In a statement, President Biden called the attack “unconscionable” and warned Israel’s enemies not to take further advantage of this moment.

Said Cook: “It seems that the United States, by dint of [Biden’s] public statement, is going to give the Israelis a lot of leeway to respond. Given the number of Israel casualties, no one external power is going to have leverage on the Israelis in the short term.”

Bradley Peniston contributed to this report.