'Every cab driver in Israel knows that Nasrallah is a man who keeps his promises,' Israel's Yediot Ahronoth daily admitted on Thursday.

The ominous aspect of that for Israelis is that Sheikh Nasrallah - whose forces have killed 29 Israeli civilians and soldiers, and even disabled a navy ship, during the first eight days of fighting - has said he has more 'surprises' in store. In a speech last Sunday, he referred to the killing of eight Israelis in the Haifa missile strike.

'As long as the enemy has no limits, we will have no limits,' said Sheikh Nasrallah, which means victory of God in Arabic. But his confrontation with Israel has come at enormous cost to Lebanon, with more than 300 people, mostly civilians, killed in air strikes that have ravaged the country's infrastructure.

Death at the hands of Israel is not an abstraction to Sheikh Nasrallah, whose eldest son, Hadi, was killed in combat with Israeli troops in 1997.

Sheikh Nasrallah is the eldest son of a poor grocer who had nine children. He moved from southern Lebanon to the Iraqi city of Najaf in his late teens to study in a religious seminary. His mentor there, and when he moved back to Lebanon in 1978, was Abbas Musawi, with whom he later founded Hezbollah as a radical, fundamentalist movement within the disadvantaged Shi'ite Muslim community.

The turning point for Hezbollah came in 1982, when Israel invaded Lebanon in a bid to smash the Palestine Liberation Organisation, at the cost of enormous fatalities and destruction. The occupation further radicalised what had been for many years a quiescent community.

Musawi, Hezbollah's secretary-general, was assassinated in an Israeli helicopter strike in 1992, and Sheikh Nasrallah took up the mantle of leadership.

When his son fell in battle five years later, he refused to accept condolences, saying that he was 'gratified'.

'It would be a lie for me to say the loss of my son does not pain me, but he was killed as a martyr, and this is the most gratifying feeling a father can have,' he said. 'According to our tradition, the beautiful life of a martyr begins in paradise. He enjoys a special place next to God, and the martyr has a special right to demand conditions for his family when their time comes. Hadi will assure us a place in paradise and this is the highest level of gratification.'

Sheikh Nasrallah's faith is intertwined with a revolutionary zeal that analysts believe partly drove him to keep conflict with Israel simmering, even after it withdrew from the south, and to initiate last week's abduction of two Israeli soldiers.

'For him, the conflict is existential,' said Tel Aviv University historian Bruce Maddy-Weitzman. 'He doesn't accept the American order and [its] plans for democratisation in the region.'

To Sheikh Nasrallah, the UN Security Council resolution calling for the disarming of Hezbollah is integral to US plans.

Although he recognises he cannot bring about an Islamic state in Lebanon during his lifetime, partly because of the country's large Christian population, he still believes 'in a pan-Islamic ideology that views the region as Muslim land where the only legitimate governments are Muslim governments', said Dr Maddy-Weitzman.

Sheikh Nasrallah's prestige peaked with the Israeli withdrawal from Lebanon in 2000, and he became a hero and inspiration to many in the Arab world.

With Iranian help, he built up Hezbollah's social welfare institutions and military capability, and oversaw its entry into parliamentary politics. His charisma and rhetorical ability stand out when compared with other Lebanese politicians.

'He's younger than they are, better looking, and a very serious winner of hearts for Hezbollah,' said Moti Kedar, of Bar Ilan University, near Tel Aviv.

But the internal equation began to turn against Sheikh Nasrallah last year, with growing calls to follow up the withdrawal of Syrian troops from Lebanon with the disarming of Hezbollah.

Hezbollah's two patrons, Iran and Syria, meanwhile, were coming under UN pressure: Iran for its nuclear programme, and Syria due to the investigation into the assassination of former Lebanese prime minister Rafik Hariri.

Sheikh Nasrallah, who in 2004 elicited an Israeli trade of hundreds of prisoners for several captured soldiers, thought he could do so again. He also appears to have been influenced by the Israeli Army operations launched against Hamas in Gaza last month, which provided him with a chance to burnish his credentials as a supporter of the Palestinian cause.

These factors are believed to have played a role in his ordering the cross-border raid and abduction that triggered the fresh fighting.

Israeli leaders are convinced he made a fateful miscalculation and failed to foresee the magnitude of Israel's response. The army's premise is that the onslaught will turn Lebanon against Sheikh Nasrallah, leading to his political demise, even if his physical removal cannot be orchestrated. But whether he will emerge weakened or strengthened from the fighting is in the eye of the beholder.

Khaled Amayreh, a Palestinian journalist in the West Bank city of Hebron, said Sheikh Nasrallah was standing out as a much more formidable fighter against Israel than Arab regimes have traditionally been. 'Hezbollah has been able to put up a very real resistance,' he said. 'In the 1960s, '70s and '80s, Israel confronted cowardly Arabs who fled, but it now faces a new situation of fighting against Islamists with deep religious convictions who are not intimidated.'

Nadim Shehadeh, of London's Chatham House think-tank, said Hezbollah's argument that it needed weapons was being underscored by Israel's offensive, and if he survives, Sheikh Nasrallah will emerge strengthened from the fighting.

'Nasrallah may have made a miscalculation, but the real problem here is a flaw in Israeli doctrine. They think that if they pound Lebanon enough, more people will turn against Hezbollah. Experience has shown this does not work. The average Shi'ite farmer in southern Lebanon was under Israeli occupation for 22 years and regards Hezbollah as a liberator. Israel is now on a pointless rampage.'

But Dr Maddy-Weitzman said that while people may instinctively identify with Sheikh Nasrallah amid the conflict: 'I don't think that when the dust settles they'll say this was a good thing.'

His death would by no means spell the end of Hezbollah, in the view of Zvi Barel, commentator for Israel's Haaretz newspaper. It would probably maintain its cohesion and a new leader would be chosen, he said.

The real question is whether any successor would have Sheikh Nasrallah's organisational skills, military intuition and political acumen.

'It is hard to answer whether someone can fill his shoes, but it is possible a new leader will grow with the job, as Nasrallah himself did,' Mr Barel said.