The New York Times reported Sunday that days after Hamas attacked Israel on October 7, 2023, the Pentagon quietly sent several dozen commandos to Israel to help advise on hostage recovery efforts, U.S. officials said.

The JSOC forces were quickly joined by a group of intelligence officers, some working with the commandos in Israel and others at the CIA headquarters at Langley, Virginia, near Washington, DC.

For more than a year, much of the attention and criticism about U.S. support for Israel has focused on the American-made bombs and weapons that Israel has used to attack Gaza. But intelligence assistance to Israel has also been crucial. U.S. intelligence helped locate the four hostages rescued by Israeli commandos in June.

Almost from the beginning of the war, American military and intelligence cells focused not only on the search for hostages, but also on hunting down senior Hamas leaders.

Senior American leaders do not claim credit for the Israeli operation that killed Hamas leader Yahya Sinwar, the architect of the October 7 attack. But they say their intelligence helped in the hunt.

“Shortly after the October 7 massacre, I directed our special operations personnel and intelligence professionals to work alongside their Israeli counterparts to help locate and track Sinwar and other Hamas leaders hiding in Gaza,” US President Joe Biden said in a statement on Thursday after Israel announced it had killed Mr. Sinwar.

According to senior officials, during the course of the war in Gaza, American “fusion cells” shifted their focus based on the latest actionable intelligence. Sometimes the best tips were on the locations of hostages. At other times, the cells focused on the whereabouts of Hamas leaders. But neither mission was ever sidelined.

The two American intelligence analysis groups, in Israel and at CIA headquarters, regularly exchanged information and insights.

Defense officials insisted they did not directly support Israeli military operations on the ground in Gaza, a campaign that has killed tens of thousands of Palestinian civilians and reduced the area to rubble, but officials said the hunt for senior Hamas leaders was different, the newspaper reported.

“Hamas-led groups held about 250 hostages in attacks last year, including Americans. Mr. Sinwar and other senior Hamas leaders kept the captives close by, hoping to deter Israeli attempts to kill them with a bombing strike. Hamas leaders issued standing orders to shoot the hostages if Israeli forces were discovered nearby, a strategy designed to deter Israeli commando teams from entering the tunnel network where Mr. Sinwar was long believed to be hiding.”

Since the start of the more than year-long war, U.S. military officials have said that the search for the hostages has been their primary mission in Israel. But senior administration officials have described the search for the hostages and the Hamas leaders as intertwined.

It is noteworthy that in an interview conducted earlier this year, National Security Advisor Jake Sullivan said that “the US military and spy agencies gained experience in finding high-value targets from the pursuit of Osama bin Laden and other terrorists in Iraq and Afghanistan that was useful to the Israelis.”

“We have been using this expertise since the first weeks after October 7,” Mr. Sullivan said.

Senior White House officials have met regularly with William J. Burns, the CIA director, and Lloyd Austin III, the defense secretary, about what additional support targeting cells might need to accelerate the hunt for Mr. Sinwar, U.S. officials said.

Officials did not disclose many details about what kind of intelligence the cells provided to Israel.

At least six MQ-9 Reapers, operated by U.S. special operations forces, flew missions to help locate the hostages, monitor for signs of life and pass possible leads to the Israeli military, the officials said.

The drones cannot map Hamas’s vast underground tunnel network — Israel uses top-secret ground sensors to do that — but its infrared radar can detect the heat signatures of people entering or leaving the tunnels from above ground, officials said.

In the end, it was a random Israeli unit on patrol in southern Gaza that discovered Sinwar by chance, the highest-value target of all.

No U.S. forces were directly involved in the operation that killed the Hamas leader, Pentagon spokesman Maj. Gen. Patrick S. Ryder said Thursday. “This was an Israeli operation,” he said.

But American officials insist that the United States helped gather intelligence that helped the Israeli military narrow its search.

In the weeks since Hamas killed a group of hostages in tunnels in Rafah in southern Gaza, American and Israeli intelligence agencies have focused on the area, believing that this might be where Mr. Sinwar is hiding.