Watch Jeremy Bowen's interview with Hezbollah

The Hezbollah fighters may not be an official army, but they look like professionals. With weapons, training and orders coming from Syria and Iran, they have shaken Israeli confidence to the extent that Israel is considering ending its occupation of southern Lebanon.

Expelling Israeli forces from Lebanon is precisely Hezbollah's aim.

One officer, speaking on condition of anonymity, attributes Hezbollah's success to "hard work, and long and brutal experience of the Israeli army"

"Our men are devout Muslims," he adds. "We'll have victory or martyrdom."

Sheikh Kassem: "Force is what works with Israel"

Israel denounces Hezbollah as a terrorist force. Hezbollah leader Sheikh Naim Kassem maintains his men are not terrorists but a legitimate force fighting an illegal occupation of Lebanese territory by Israel.

A roadside bombing by Hezbollah in November killed three Israeli soldiers, and a further four Israeli troops have died in the conflict since then.

Israel in turn estimates it has killed 60 Hezbollah fighters this year. But the Hezbollah officer who spoke to the BBC believes there are enough willing volunteers to continue waging war. He also believes the Israelis are losing heart.

Although the Lebanese government does not control Hezbollah, it approves of the force's aim of ending the Israeli occupation.

Concern in Beirut

But Rafik Hariri, who is about to leave office after six years as Lebanese prime minister, fears that Hezbollah activities may be seized on by Israel as an excuse for counterstrikes against Lebanon.

"If anything happens on the Israeli border, Lebanon is held accountable, and then Israel will have a free hand to do whatever they want," Mr Hariri says.

The Israelis "are stronger than us, they can do anything," he fears.

Hezbollah itself is more confident.