ISRAELI HIT-LIST: After Mohammed Deif, who is 2nd most-wanted Hamas mastermind Yahya Sinwar?

Israel has two alleged Hamas masterminds of the attacks on October 7 at the top of its hit list, while Tel Aviv has threatened to kill every member of the Hamas group if it invades Gaza.

Military strategist Mohammed Deif and political leader Yahya Sinwar have already spent time in Israeli or Palestinian jails and been the targets of multiple assassination attempts.

The hunt for the two most senior Hamas leaders in the beleaguered Gaza Strip will be fierce this time.

In the war of words leading up to the impending ground offensive, Israel has said that Sinwar is "a dead man walking".

At least 3,785 Palestinians and more than 1,400 Israelis have lost their lives in the ongoing Israel-Hamas war.

"Hamas terrorists have two options: Be killed or surrender unconditionally. There is no third option," Defence Minister Yoav Gallant said.

Hamas spokesmen have responded that the Palestinian group is "not scared".

Security sources outside Gaza say Deif and Sinwar have been embedded in the enclave's network of tunnels — built to resist Israel´s air assault — since hundreds of Hamas fighters crossed the border to hit kibbutz communities, towns and military bases.

But even before the latest Hamas assault, the pair spent years operating in the shadows.

Israel has particularly singled out the 61-year-old Sinwar who was elected Hamas leader in Gaza in 2017 after Ismail Haniyeh went into exile.

Israeli military spokesman Lieutenant Colonel Richard Hecht called Sinwar the "face of evil" and declared him a "dead man walking".

Sinwar was one of the founding members of Hamas during the first Palestinian intifada, or uprising, in 1987 and rose through the ranks as a fierce advocate of armed struggle.

A graduate of the Islamic University in Gaza, Sinwar learned Hebrew while spending 23 years in Israeli jails.

He was serving four life terms for the killing of two Israeli soldiers when in 2011 he became the most senior of 1,000 Palestinians released in exchange for the French-Israeli soldier Gilad Shalit.

In the shadows

Sinwar and Deif were both born in the Khan Yunis refugee camp in Gaza and both were added in 2015 to the United States´ list of most wanted "international terrorists".

Hamas is also branded a terrorist organisation by the United States and European Union.

Much less is known however about Deif, Israel's number one public enemy for the past two decades during which he has been accused of organising suicide attacks, kidnappings and other raids.

There is only one known full-face photo of the chief of the Ezzedine al-Qassam Brigades, Hamas's military wing, which is at least 20 years old. The others show him either in a mask or standing in the shadows to avoid identification.

An audio message from Deif was transmitted by Hamas media on the morning of the attacks which were dubbed "Operation Al-Aqsa Flood".

"The rage of our people and our nation is exploding," he said.

Deif was born Mohammed Diab al-Masri in 1965.

His assumed name means "Guest" in Arabic and he reportedly never spends more than one night in the same place. Enemies have dubbed him the "cat with nine lives" as he has faced at least six failed assassination attempts.

Deif's wife and at least one child were killed in an Israeli air strike during the 2014 Gaza war. Deif has reportedly lost one eye and been disabled by the various attempts but it has not weakened his influence.

He has been involved with Hamas since the 1980s and was arrested at the start of the second intifada but escaped, or was released, from a Palestinian Authority prison in 2000. He became head of the Hamas military wing in 2002 and has been Israel´s bete noire ever since.

Israel has sent a firestorm of warnings to the Hamas leaders on top of the thousands of airstrikes since October 7.

"Every member of Hamas is a dead man," said Prime Minister Benjamin Netanyahu.

However, experts say that eliminating Sinwar and Deif would severely weaken but not crush Hamas, which is Israel´s declared aim.

"Sinwar and Deif are clearly first priority leadership, the loss of which would damage Hamas, but one presumes that the group has contingencies about their loss," said H.A. Hellyer, an international security specialist at the Royal United Services Institute in London.