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In 2021, shortly after the fourth war between Hamas and Israel since 2008, the group's enigmatic leader Yahya Sinwar openly challenged Israel to assassinate him during a live news conference in Gaza.
“When I am done here, I will be walking for most of my journey home,” he said.
“I will wrap this up in 10 minutes and it will take me another 10 minutes to get ready to leave, then I will walk for 20 or 30 minutes. That's nearly one hour or 3,600 seconds; enough for Israel to weaponise an aircraft and launch it,” he taunted Israel.
“Yet, I will not bat an eyelid,” boasted Mr Sinwar.
Shortly after the news conference, Palestinian television networks aired footage of the grey-haired Hamas leader confidently walking the streets of Gaza, surrounded by aides and security guards while joyfully greeting and shaking hands with his supporters.
Press forward to December 2023 and Mr Sinwar, who had not been seen in public in about a year, remains top of Israel's most wanted list and continues to elude being killed or captured.
However, the manhunt this time is more urgent since the Hamas leader is known to have been among the chief architects of the militant group's surprise October 7 attack on southern Israel, when its fighters killed about 1,200 Israelis – giving Israel its deadliest day since its creation in 1948 – and taking about 240 hostages back to Gaza.
The attack drew a harsh response from Israel, with bombardment of Gaza and ground operations killing more than 17,700 Palestinians, displacing the majority of the territory's 2.3 million residents and razing to the ground large swathes of built-up areas in the tiny and densely-populated coastal enclave.
Egyptian security sources with years of experience dealing with Hamas leaders and Israel say Mr Sinwar, along with other top Hamas leaders, are now facing an elaborate and tireless kill-or-capture manhunt by elite Israeli troops operating in southern Gaza, including men from the combat-seasoned 98th Division.
Israeli Prime Minister Benjamin Netanyahu boasted last week that there was no place in Gaza that Israel cannot reach. “Getting him is just a matter of time,” said the Israeli leader about Mr Sinwar whose home in the southern Gaza city of Khan Younis was besieged by Israeli troops last week.
As expected, Mr Sinwar wasn't there.
Alongside troops on the ground, Israel's manhunt involves drones equipped with sophisticated eavesdropping devices, according to the sources. Israel is also using intelligence gathered by its network of Palestinian spies, whose collaboration with the “enemy” is believed to have facilitated the assassination of several Hamas leaders by Israel, including its founding father and spiritual leader Sheikh Ahmed Yassin.
Israeli security officials have also extensively questioned hostages released by Hamas as part of a week-long truce that collapsed on December 1, hoping they could have heard or seen anything that might help them track down Mr Sinwar, said the sources.
Doctors and other medical staff from Gaza's main Al Shafaa hospital, long suspected by Israel to be sitting on top of a major underground Hamas command centre, have also been interrogated by the Israelis to glean any clues on Mr Sinwar and his top aides.
Besides Mr Sinwar, Israel's most wanted list includes other leaders of the militant group like Mohammed Al Deif, Marwan Issa, Yahya Moshtahy, Abdullah Al Barghouti and Fathy Hamad, according to the officials.
The sources said capturing Mr Sinwar has become a focus of Mr Netanyahu and his government, described as the most right-wing to take office in Israel's history.
Killing or capturing him will gift the Israeli leader considerable political leverage if the time comes for him to face a possible inquiry into the intelligence and security failure that saw Hamas fighters meet little resistance as they rampaged through southern Israel for hours on October 7.
“I think Israel will probably end its military operations in Gaza if he's captured,” said one of the sources.
Assassinating Mr Sinwar will add his name to a long list of top Hamas leaders or senior field commanders assassinated by Israel. Most prominent on the list are Abdel Aziz Al Rantisi, the co-founder of Hamas in 2004, and Ismail Abu Shanab, also a co-founder of Hamas and one of its main three leaders in Gaza in 2003. Yassin was killed in 2004 by rockets fired by an Israeli helicopter as he left a mosque near his home.
But the security-conscious Mr Sinwar, who helped found Hamas in the 1980s, may not be an easy target.
Last month, Egyptian officials said Mr Sinwar occasionally stopped taking calls for days, during the negotiations that led to the week-long truce, because of security concerns. He routinely had aides schedule calls from Egyptian and Qatari mediators or fellow Hamas leaders like Ismail Haniyeh, they said.
He used secure lines that he would frequently change and sophisticated jamming devices to avoid exposing his location to the Israelis. He often communicated with Hamas's field commanders through coded written messages, the officials said.
Throughout the negotiations, Mr Al Sinwar used coded language for the day and time he would make or receive calls. He also used different aliases, the officials said.
The story of Mr Sinwar's rise to the leadership of Hamas in 2017 speaks of a man's unconditional dedication to the Palestinian cause but also conceived brutality. He used his 23-year incarceration in Israel to gain knowledge that helped him climb his way up to group's leadership in 2017.
It is in his native of Khan Younis, where the Israeli ground offensive is currently focused, that Mr Sinwar earned the unflattering nickname “Butcher of Khan Younis” for tracking down Palestinian spies and executing them after summary trials.
An Arabic language graduate from Gaza's Islamic University, he was detained twice by Israel before he was sentenced to life in prison in 1989 for killing Israeli soldiers and Palestinian spies.
He learnt and mastered Hebrew while in jail, allowing him to study Israel's society, politics and media. He was reportedly interrogated for 180 hours while in detention and declined repeated Israeli offers to become a double agent.
He had brain tumour while in jail, but was saved by Israeli surgeons who removed it.
When reportedly told by one of his doctors of the paradox of being saved by doctors from the country he wanted to destroy, his response was that it was their duty to do so.
Mr Sinwar was released from prison in 2011 as part of a prisoners' swap that freed 1,027 mostly Palestinian prisoners held in Israeli jails in return for Gilad Shalit, an Israeli soldier held captive by Hamas for more than five years.
Realising early that he was likely to be included in the 2011 prisoners' swap, Mr Sinwar publicly disavowed violence while incarcerated and persuaded his jailers that he was no longer interested in politics, according to some accounts.
