The appointment of Yahya Shinwar as Hamas’ supreme leader formalizes a role he assumed in the early hours of October 7when the surprise attack on Israel, which he is believed to have masterminded, led to the bloodiest chapter of the Israeli-Palestinian conflict.

He is seen as a hardliner with closer ties to Hamas’ armed wing than his predecessor, Ismail Haniya, who was assassinated in the Iranian capital last month. Iran blames Israel for his death and the conflict between the two has heightened fears of sparking a wide-ranging regional war.

Yahya Sinuart was considered to already have the final word on any Gaza ceasefire agreement and the release of dozens of Israeli hostages still held by Hamas.

But unlike Ismail Haniya, who lived in Qatar, Sinwar is hiding deep inside Gaza, and mediators say it takes several days to exchange messages with him. This raises questions about how he will manage Hamas, an organization with operatives across the Middle East.

Hamas has survived the assassination of several top leaders for more than three decades while maintaining a high degree of internal cohesion – and the selection of Sinwar, who is at the top of Israel’s most-wanted list, is seen by many as a sign of defiance.

But Hamas has never faced a crisis of this magnitude – and the man who created it is now tasked with managing the fallout.

Even tougher attitude towards Israel

Haniya was a veteran of the political wing of Hamas, who had once served as prime minister of Palestine and in recent years had been managing Hamas affairs from his base in Qatar.

While Hamas has always supported armed struggle, Haniya and other exiled leaders have occasionally expressed a more moderate tone, even leaving open the possibility of accepting a possible two-state solution, although they have formally refused to recognize Israel.

Sinwar, by contrast, spent more than two decades in Israeli prisons and told interrogators that he had killed 12 Palestinians suspected of collaborating with Israel, gaining a reputation for cruelty among both Palestinians and Israelis.

He and the Mohammed Daifthe shadowy head of Hamas’ armed wing that Israel claims it killed in a recent strike, have spent years building up the group’s military power and are believed to be the masterminds of the October 7 attack.

In the recent negotiations, “Haniya had played a big role in trying to get Sinwar to accept a cease-fire proposal with Israel,” said Hugh Lovatt, an expert on the Israeli-Palestinian conflict at the European Council on Foreign Relations.

Sinwar has insisted on demands for the release of hundreds of Palestinian prisoners, the full withdrawal of Israeli forces from Gaza and a lasting ceasefire — even as nearly 40,000 Palestinians have been killed in the ongoing war, which has devastated much of the region.

Israeli Prime Minister Benjamin Netanyahu has vowed to continue the war until Hamas is completely destroyed and all hostages return home.

“The assassination of Haniya has already set the negotiations back,” says Lina Khatib, a Middle East specialist at London-based think tank Chatham House. “This move by Hamas makes negotiations even more difficult.”

Sadeq Abu Amer, head of the Palestinian Dialogue Group, a Turkey-based think tank, said that while the emergence of Sinwar may appear to be a “challenge to Israel,” a deal remains possible. “Sinouar, in his new role, can take a step that will surprise everyone,” he adds.

He hides in the shadows

Predicting how Sinwar will lead Hamas is difficult because of the secrecy surrounding him.

Sinouar has not been seen since the beginning of the war, and even before October 7 he had made only rare public appearances. He is likely to be hiding deep within the Hamas tunnel network and is largely cut off from the outside world.

While he can be expected to set overall policy and make the final decision on any ceasefire agreement, Hamas’ day-to-day operations in the Israeli-occupied West Bank and elsewhere are likely to be managed by its exiled leaders in Qatar, the Lebanon, Turkey and Iran.

“There are issues that he can make a decision on and there are issues that his deputies and the rest of the politburo can decide on,” said Hani al-Masri, a veteran Palestinian analyst who has met most of the of Hamas leaders, including Haniya and Sinwar.

Hamas has a long history of persistence after the assassination of its top leaders – including its founder and spiritual leader, Sheikh Ahmed Yassin, who was killed in an airstrike in 2004.

But it has never faced a campaign of targeted killings on such a scale.

Israel says it has killed several Hamas commanders in Gaza, including Daif, whose death Hamas has neither confirmed nor denied. Another top Hamas leader, Saleh Aruri, was killed in an Israeli airstrike in Beirut in January. The series of targeted killings likely led other Hamas leaders to curtail their movements and contacts.

That could ultimately undermine the organization, even though it enjoys the support of many—but not most—Palestinians.

“Israel’s elimination of senior Hamas leaders who cannot easily be replaced likely had a qualitative impact on the movement,” Lovat said. “More fundamentally, however, the assassination of high-ranking figures such as Aruri and Haniya appears to have taken the movement in a more violent direction.”