LONDON — His nom de guerre "Deif" means "guest" in Arabic — a reference to his habit of staying in a different house each night to evade Israeli attacks. Mohammed Deif is the elusive head of Hamas' military wing and the man believed to be behind the group's unprecedented Oct. 7 attack on Israel.

Within hours of the attack, a recorded statement was released by a Hamas TV channel, according to Reuters, claiming to show Deif. "Enough is enough," the figure in the video said, appearing as a silhouette. He announced the beginning of what he called "Operation Al-Aqsa Storm," a reference to the mosque in Jerusalem, Islam's third-holiest site, where Israelis have carried out recent raids.

The death toll from Saturday's attack — in which Hamas militants entered Israel from Gaza on paragliders and broke through a barrier fence, killing and kidnapping people — has reached 1,300. An estimated 150 people were kidnapped from Israel and taken hostage.

Israel's ongoing retaliatory offensive on the Gaza Strip has so far killed 1,500 Palestinians. Israel gave an order Thursday for more than 1 million people living in northern Gaza to evacuate the area.

Here is what to know about the man believed to have masterminded the attack.

Who is Mohammed Deif?

Much about Deif's early life is unknown or unconfirmed. According to reports by international media outlets, Deif was born in the Khan Younis refugee camp in southern Gaza in the early 1960s. The European Council on Foreign Relations says Deif was born in Gaza in 1965.

Some reports say Deif was part of a theater group called The Returners while a university student in Gaza. Avi Melamed, a Middle East expert at the Eisenhower Institute, told the Washington Post this was something Deif kept up even after joining Hamas, sometimes acting parts in the group's propaganda videos.

Deif joined Hamas around the time of the first intifada or Palestinian uprising in 1987, and was arrested by Israel for his activities in 1989, a Hamas source told Reuters. He spent more than a year in an Israeli jail but returned to Gaza in the early 1990s, when he began rising quickly in the Hamas ranks.

"He has been active in Hamas for decades. Even before 10/7, he was a wanted man. Now after, he's even more of a wanted man," says Raphael Cohen of the RAND Corporation.

"We know he's masterminded other large scale terrorist attacks," Cohen says.

Deif has been accused of overseeing several suicide bombings, killing dozens of Israelis, from 1995 onward.

He became the head of Hamas' military wing, the al-Qassam Brigades, in July 2002, after Israel assassinated its former leader, Saleh Shehada. Since then, Deif has become known as the architect of Hamas' military strategy.

The State Department has designated Deif as a terrorist and he has long been on Israel's most wanted list.

"He has been subject to a number of previous Israeli assassination attempts," says Hugh Lovatt, senior policy fellow with the Middle East and North Africa program at the European Council on Foreign Relations, who has researched and written about Deif's life. "These have left him — according to some rumors — disfigured or partially paralyzed. He has also lost family members in the attacks. He does appear to have borne the brunt of Israeli attacks against him."

According to some reports, the assassination attempts left Deif blind in one eye and resulted in the amputation of some of his limbs.

During the 2014 Israel-Hamas war, Deif's wife and one of his children were killed in an Israeli-targeted airstrike on a house in Gaza that was aimed at assassinating him.

Deif — who has also been nicknamed "the cat with nine lives" — was not in the building at the time and evaded the attempt on his life.

Deif has led a shift in Hamas power, from political to military

Now the military commander spends all of his time sheltering from Israeli attacks and potential assassination, says Lovatt.

"The fact that he has personally been injured, the fact that he has lost family members in Israeli attacks, the fact that he spends his whole time in bunkers in Gaza, probably does a lot to shape his mentality," he says. "A bunker mentality, quite literally."

Lovatt says this helps in understanding the severity of Hamas' latest attack on Israel — and the direction Hamas is taking.

"This was something organized by Hamas' military leadership, without the political leadership knowing about it until quite recently," he says. "In some ways, this is a military takeover of Hamas. This is clearly where the center of power is, in the way it hasn't been for some time."

And, Lovatt says, Deif is at the center of this strategic shift.

"The question, though, is what happens to Hamas in the weeks to come," he says. "If the view within the movement is that this didn't work, there will be a shift in the power dynamics."

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