Hamas's top military commander Mohammed Deif, who has survived assassination attempts and defied the Middle East's most powerful forces, is proving a redoubtable foe for Israel in its latest incursion in Gaza.
As Israel presses its deadly offensive aimed at halting militant rocket fire and eliminating Hamas's tunnel network, Deif has warned there will be no truce in the Palestinian enclave until Israel ends its eight-year blockade.
Born in the Khan Yunis refugee camp in southern Gaza in 1965, Deif has been involved in Hamas's operations for more than 20 years, plotting suicide bombings inside Israel, kidnapping soldiers, firing rockets and helping plan the tunnels used to launch attacks.
He was appointed head of Hamas's military wing, the Ezzedine al-Qassam Brigades, in 2002 after the death of his predecessor, Salah Shehade, in a raid.
But Deif had had a long yet shadowy career as a militant before then.
His involvement with the Islamist movement in Gaza began in the 1980s when, as a biology student close to the Muslim Brotherhood, he headed the Islamists' union at Gaza Islamic University.
With the eruption of the second Palestinian Intifada in 2000, he escaped, or was freed, from a prison run by Yasser Arafat's Palestinian Authority.
His escape -- or liberation, as it is unclear whether he was freed or not -- angered the Israelis, who had had him in their sights for more than a decade by then.
Shortly after he was named Hamas's military head, Israel launched its fifth bid to assassinate him in Gaza.
That attack left him severely wounded, and some rumours suggested he had been left paraplegic, although these were never confirmed, largely due to the secrecy surrounding the details of his life.
He delegated the leadership of the brigades to his deputy, Ahmed Jaabari, thus earning the nickname the "cat with nine lives" among his enemies, and cementing his reputation inside Gaza.
Signup to our newsletter and follow us on Facebook and Twitter!
- Master of disguise -
Only a few, poor-quality photographs of Deif are known to exist, the most recent taken some 20 years ago.
His hiding place is unknown, and he is reported to be a master of disguise who is able to blend seemlessly into the population.
The mysterious commander also uses no techonology that might allow the Israelis to track him, a Hamas official told AFP on condition of anonymity.
He may have learned caution from the death of his mentor, Yahya Ayash, who was killed in 1996 by a mobile telephone booby-trapped with explosives by Israeli secret services.
Deif's real name is Mohammed Diab al-Masri, and he owes his 'nom de guerre', which is Arabic for guest, to his habit of constantly changing his location, the Hamas official said.
He descrubed Deif as a man who is "polite, discreet, softly spoken" and fascinated by "military strategy".
The elusive leader's public statements are extremely rare. In 2012, he warned Israel against launching the operation "Pillar of Defence", which was aimed at halting rockets fired by militants in the Gaza Strip.
After the death of his mentor Ayash, who passed on his explosive-making expertise, he took on the role of "engineer for the Ezzedine al-Qassam brigades", the Israeli army says in its blog.
The Israelis see him as "the brains" behind the campaign of suicide bombings that targeted buses and public places in Tel Aviv and Jerusalem until 2006 and consider him "personally responsible for the deaths of dozens of civilians".
He also played a key role in the strategic development of Hamas, the Israelis say.
They claim that Deif was among the militants "who designed the Qassam rockets" -- the Islamist movement's signature weapon that had a range of eight kilometres (five miles) until Iran supplied them with more advanced weapons.