Around a week ago, the political leader of Hamas, Ismail Haniyeh, was assassinated in Tehran. Now the radical Islamic Palestinian group — classified as a terrorist organization by Germany, the European Union, the US and other countries — has appointed 61-year-old Yahya Sinwar as his successor.

Who is Yahya Sinwar?

Sinwar has been Hamas' Gaza leader since 2017. His whereabouts in the territory are currently unknown, though it is assumed that he is hiding in Hamas tunnels under the coastal area. On Tuesday, Hamas declared Sinwar will head the organization's political bureau. His predecessor, Haniyeh, was based in the Qatari capital, Doha, and was considered Hamas' chief diplomat.

Sinwar is considered to be the mastermind behind Hamas' brutal attacks on Israel on October 7, 2023, in which around 1,200 people were killed in the country's south, with over 250 people taken back to Gaza as hostages. In response, Israel took massive military action against targets in Gaza. According to the Hamas-controlled Health Ministry, more than 39,650 people have been killed so far, a figure that cannot be independently verified.

Sinwar's role in the terrorist attack made him one of the organization's most wanted leaders. He is very popular among the Palestinians and is seen as the "spearhead of armed resistance" against Israel, said Israeli security expert Kobi Michael from the Institute for National Security Studies at Tel Aviv University.

Sinwar has not appeared in public since October 7.

'Butcher of Khan Younis'

Sinwar was born in 1962 in southern Gaza's Khan Younis refugee camp. His family comes from the area around the coastal town of Ashkelon, which is now part of Israeli territory.

When Hamas was formed during the first Palestinian uprising, the intifada, at the end of the 1980s in the fight against Israeli occupation, Sinwar contributed to setting up Hamas' military wing, the Qassam Brigades. In the early years of Hamas' existence, he was responsible for the fight against individuals within the organization's own ranks suspected of collaborating with Israel. Sinwar was so brutal that he became known as the "Butcher of Khan Younis."

He was later handed four life sentences for killing two Israeli soldiers and several Palestinians who he suspected of collaboration. Sinwar spent a total of 22 years in Israeli prison, during which he is said to have learned Hebrew. He was released in 2011 by Israeli Prime Minister Benjamin Netanyahu as part of a prisoner exchange.

What can we expect from Sinwar as Hamas leader?

It's known that Sinwar wants to achieve a unified Palestinian leadership across all Palestinian territories, including the occupied West Bank, which is governed by Palestinian President Mahmoud Abbas' Fatah party, which rivals Hamas.

Sinwar is the main decision-maker when it comes to exchanging hostages and reaching a cease-fire with Israel. Yet he could be more opposed to a cease-fire agreement in Gaza than his predecessor Haniyeh, experts believe.

Security expert Michael said Hamas' announcement to put Sinwar in charge sent a "strong message" to Israel that Hamas is "continuing on its path of resistance."

The appointment of Sinwar, who is considered more extreme than his predecessor Haniyeh, can be interpreted as a demonstration of power, said Michael. On the other hand, Sinwar's rise to power could also offer new opportunities, he added.

"Sinwar cannot lead Hamas from the Gaza tunnel where he is hiding. As a political leader, he must operate from outside Gaza. And he can't get out without a hostage agreement or a cease-fire in place."

This article was originally written in German.

Correction: This article has been updated to correct the details of Sinwar's prison sentence.