By Nidal al-Mughrabi

Jan 7 (Reuters) - Mohammad Sinwar, the elusive Hamas military chief in Gaza, had for months since the death of his brother, in 2024, been Israel's most wanted man. On December 29, Hamas announced that he had died, aged 49, around seven months after Israel said it killed him in a strike.

Hamas did not provide details on Sinwar's death but said it mourned him along with other group leaders, describing them as "heroic martyrs". Hamas confirmed in the statement that Sinwar had been the head of the group's armed forces.

Sinwar was elevated to the top ranks of Hamas in 2024 after the death in combat of his brother Yahya, mastermind of the October 2023 attack on Israel that led to the war in Gaza and later overall leader of the Palestinian organisation.

Israeli Prime Minister Benjamin Netanyahu said in May 2025 that Sinwar had been killed. Less than two weeks later, the Israeli army said it had retrieved Sinwar's body in an underground tunnel beneath a hospital in southern Gaza.

Sinwar's death is expected to leave his next in command Izzeldeen Haddad, who had been overseeing operations in northern Gaza, in charge of Hamas' armed wing across the whole of the enclave.

It is unclear how the death will affect decision-making in Hamas more broadly - for example, whether it will bolster or diminish the influence of exiled members of the group's leadership council on policy matters, in particular the full implementation of the Gaza ceasefire plan agreed with Israel in October.

ASSASSINATION ATTEMPTS

Hamas officials described Sinwar as a "ghost" who long outfoxed Israel's intelligence agencies.

Like his brother Yahya, Sinwar had survived many Israeli assassination attempts, including airstrikes and planted explosives, Hamas sources said. 

When Sinwar once visited a cemetery, his comrades discovered a remote-controlled explosive resembling a brick planted along his path, according to the Hamas sources.

In 2003, Hamas operatives discovered a bomb in the wall of Mohammad Sinwar's house, foiling an assassination attempt that the group blamed on Israeli intelligence.

CLANDESTINE PLOTS

Known for clandestine operations, Mohammad Sinwar played a central role in planning and executing Hamas' October 7, 2023, attack on Israel, the country's worst security failure, Hamas sources said.

He was also widely believed to have been one of the masterminds of the 2006 cross-border attack and abduction of Israeli soldier Gilad Shalit. 

Hamas held Shalit for five years before he was swapped for more than 1,000 Palestinians jailed by Israel. 

Under the deal, his brother Yahya Sinwar, whose meticulous planning for the 2023 attack shattered Israel's reputation as an invincible power in a hostile region, was among those who were released.

HAMAS WEAKENED BUT STANDING

Netanyahu has vowed to eradicate Hamas. The offensive against Gaza by the Israeli Defence Forces, the Middle East's most advanced military, severely weakened the organisation. 

Yahya Sinwar was killed in combat during a routine Israeli patrol in Gaza in 2024.

Israel released footage of a severely wounded Yahya Sinwar throwing a piece of wood at a hovering drone - his last act of defiance towards his old foe before his death and his brother's rise. 

But the group, which was created during the first Palestinian uprising against Israeli occupation in 1987 and which carried out suicide bombings that traumatised Israelis in the second one, is still standing.

FROM REFUGEE TO HARDLINER

Born on September 16, 1975, Sinwar rarely appeared in public or spoke to the media. He granted a lengthy interview to Al Jazeera for a documentary broadcast in 2022, but wore a cap and sat in the dark to hide his appearance.

The Sinwars originally came from Asqalan - now the Israeli city of Ashkelon, a short distance to the north of the Gaza Strip. Alongside hundreds of thousands of other Palestinians, they became refugees in what they call the Nakba, or catastrophe, at the time of Israel's declaration of independence during the 1948 war.

The family settled in Khan Younis in Gaza, which has been largely reduced to rubble in the latest war. 

Mohammad Sinwar was educated in schools run by the United Nations' Palestinian relief agency (UNRWA), which has long been a target of Israeli criticism, including during the recent war in Gaza.

He joined Hamas shortly after its founding, influenced by his brother Yahya, a former member of the Muslim Brotherhood, the oldest and at one time most influential Islamist group in the Middle East. 

His reputation as a hardliner helped him rise through the group's military ranks. By 2005, he was leading Hamas' Khan Younis Brigade.

The unit, one of the largest and most powerful battalions in Hamas' armed wing, has been responsible for cross-border attacks, firing rockets and planting bombs along the frontier. “Striking Tel Aviv is easier than drinking water," Sinwar told Al Jazeera.

The unit also watches the movements of Israeli soldiers around the clock. In 2006, elite commandos led by Sinwar took part in Shalit's abduction.

Sources close to Hamas say Sinwar developed close ties with Marwan Issa, the deputy commander of Hamas' military wing, and Mohammed Deif, the aloof military chief. Both men were killed by Israel in 2024.

In its statement announcing Sinwar's death on December 29, Hamas said that he had succeeded Deif.

(Reporting by Nidal Al-Mughrabi; Writing by Tala Ramadan; Editing by Olivier Holmey and Michael Georgy)