For Israeli and Western officials, Sinwar has over the course of these negotiations, which stalled again in Cairo this past week, emerged as both a brutal adversary and a deft political operator, capable of analysing Israeli society and appearing to adapt his policies accordingly.

As an architect of the October 7 attacks, Sinwar masterminded a strategy that he knew would provoke a ferocious Israeli response. But in Hamas’ calculus, the deaths of many Palestinian civilians – who do not have access to Hamas’ subterranean tunnels – were the necessary cost of upending the status quo with Israel.

US and Israeli intelligence agencies have spent months assessing Sinwar’s motivations, according to people briefed on the intelligence. Analysts in both the United States and Israel believe that Sinwar is primarily motivated by a desire to take revenge on Israel and weaken it. The wellbeing of the Palestinian people or the establishment of a Palestinian state, the intelligence analysts say, appears to be secondary.

An understanding of Israeli society

Sinwar was born in Gaza in 1962 to a family that had fled its home, along with several hundred thousand other Palestinian Arabs who fled or were forced to flee during the wars surrounding the creation of the state of Israel.

Sinwar joined Hamas in the 1980s. He was later imprisoned for murdering Palestinians whom he accused of apostasy or collaborating with Israel, according to Israeli court records from 1989. Sinwar spent more than two decades in Israeli detention before being released in 2011, along with more than 1000 other Palestinians, in exchange for one Israeli soldier captured by Hamas. Six years later, Sinwar was elected leader of Hamas in Gaza.

While in prison, Sinwar learned Hebrew and developed an understanding of Israeli culture and society, according to fellow former inmates and Israeli officials who monitored him in prison. Sinwar now appears to be using that knowledge to sow divisions in Israeli society and heighten pressure on Benjamin Netanyahu, the Israeli prime minister, according to Israeli and US officials.

They believe that Sinwar has timed the release of videos of some Israeli hostages in order to spur public outrage at Netanyahu during crucial phases of the ceasefire talks.

Some Israelis want the remaining hostages released even if it means agreeing to Hamas’ demands for a permanent truce that would keep the group – and Sinwar – in power. But Netanyahu has been reluctant to agree to end the war, partly because of pressure from some of his right-wing allies, who have threatened to resign if the war concludes with Hamas unbroken.

If Netanyahu has been accused of dragging out the fighting for personal benefit, so, too, has his archenemy, Sinwar.

Israeli and US intelligence officers say that Sinwar’s strategy is to keep the war going for as long as it takes to shred Israel’s international reputation and to damage its relationship with its primary ally, the United States. As Israel faced intense pressure to avoid launching an operation in Rafah, Hamas fired rockets from Rafah toward a nearby border crossing, killing four Israeli soldiers.

If this was a gambit by Hamas, it appeared to pay off: Israel began an operation this last week on the fringes of Rafah, and against that backdrop US President Joe Biden made his strongest criticism of Israeli policy since the war began. B

iden said he would halt some future arms shipments if the Israeli military began a full-scale invasion of the city’s urban core.

US officials say Sinwar is most likely in the tunnels under Khan Younis, the next major city to the north – intelligence that could undercut the Israeli rationale for the military operations in Rafah.

Projecting an image of unity

Hamas and its allies deny that either Sinwar or the movement is trying to leverage further Palestinian suffering.

“Hamas’ strategy is to stop the war right now,” said Ahmed Yousef, a Hamas veteran based in Rafah. “To stop the genocide and the killing of the Palestinian people.”

US officials say that Sinwar has shown disdain for his colleagues outside Gaza, who were not informed about the precise plans for Hamas’ attack on October 7. US officials also believe that Sinwar approves military operations conducted by Hamas, although Israeli intelligence officers say they are unsure of the extent of his involvement.

A senior Western official familiar with the ceasefire negotiations believes that Sinwar appears to make decisions in concert with his brother, Muhammad, a senior Hamas military leader, and that throughout the war he had sometimes disagreed with Hamas leaders outside Gaza.

While the outside leadership has at times been more willing to compromise, Sinwar is less ready to concede ground to the Israeli negotiators, in part because he knows that he is likely to be killed whether the war ends, the official said.

Even if negotiators seal a ceasefire deal, Israel is likely to pursue Sinwar for the rest of his life, the official said.

Hamas members have projected an image of unity, downplaying Sinwar’s personal role in decision-making and maintaining that Hamas’ elected leadership collectively determines the movement’s trajectory.

Sinwar could not be reached for comment and has rarely been heard from since October. US and Israeli officials have said Sinwar is hiding near hostages, using them as human shields. An Israeli hostage who was released during a truce in November said she met Sinwar during her captivity.