Yet even as they were building their keep over the past six months, the Israelis came under fire. The Hizbollah, shooting from beside a derelict house in the village of Majdel Zoun, even managed to put a Saggar missile through a doorway, exploding it in the soldiers' kitchen.
The radar base is supposed to alert the Israelis to any hostile movement towards the Israeli border. But it is they who are being attacked inside Lebanon and it is they who are losing the war. In November alone, the Hizbollah - perhaps the most professional guerrilla force in the Middle East - and its allies mounted 170 operations against the Israeli occupiers and their untrustworthy militia allies, the so-called South Lebanon Army (SLA). One Israeli artillery base - at Sujud - was hit more than 20 times. As well as seven Israelis, they killed three SLA men and have detained yet more Israeli agents. Israel's intelligence in southern Lebanon is now effectively blind.
The most recent attacks have taken place so deep inside Israeli-occupied Lebanon, they have been carried out in sight of the border the occupation zone is supposed to protect.
The ironies lie as heavy over southern Lebanon as the fields of fire. In 1982, when General Ariel Sharon stormed in with 40,000 troops - and a total death toll of more than 17,000 Arabs, most of them civilians - they breezed up the coast from Ras al-Bayada without hindrance. Most of the Palestinians who had been firing Katyushas over the border in response to Israeli air raids around Beirut ran away. And their leader, Yasser Arafat, is now, of course, Israel's new best friend.
But the savagery of the Israeli attack created a new and wholly Lebanese resistance movement that found its recruits among the Lebanese Shia Muslims who originally welcomed the Israelis. The Hizbollah fighters didn't run away like the Palestinians. They came searching for the Israelis and drove them out of Sidon and Tyre. And now, with the Israelis desperately searching for a way of reducing their casualties - even by withdrawing from the occupation zone - the Hizbollah seem on the point of throwing them out of Lebanon altogether.
When Colonel Joiji Konrote, commander of the United Nation's first Fijian battalion came to Lebanon 20 years ago, he saw only a pathetic force of ill-trained Palestinians firing a few rounds at the Israelis before high- tailing it back to Beirut. Now General Konrote is the UN's force commander and knows all too well how the tables have been turned. Even when I walked over to talk to him at a new UN compound near Qana - replacing the base devastated in Israel's bloody massacre of refugees in 1996 - two Hizbollah mortars exploded on to an Israeli artillery base to the south.
"The ground rules have all changed," he said. "Prior to '82, we were dealing with Palestinians, but then the conflict changed and now the Israeli army is taking a lot of casualties. They are no longer dealing with a rag-tag [Palestinian] army that shoots and scoots. The Hizbollah forces are very motivated and highly trained and they are causing a lot of problems for the Israelis and the SLA." When I ask General Konrote if he could deploy his UN force down to the international border in the event of an Israeli withdrawal, his eyebrows rise suddenly.
He does not explain why. He just talks about how, with enough political will, a new mandate and sufficient material, he could lead his UN soldiers down to the frontier. But I think I know why the general's eyebrows arched so quickly. He knows - as everyone in southern Lebanon knows, including the occupying power - that the Israelis are trapped.
They still call their occupation zone a "security zone" even though it is the most insecure place in the Middle East. In a bomb attack that killed three Israeli soldiers last month, the Hizbollah actually had its own television crew taping the event deep inside the occupied area - then escaped with its film to air it on its own Beirut television station a few hours later.
So how do the Israelis staunch their wounds? For every dead soldier, says Israel's Internal Security Minister, Avigdor Kahalani, Israel should bomb Beirut, "plunging the casino of Beirut into darkness".
Actually, it is called the Casino de Liban and it is not in Beirut, but accuracy has never been Israel's forte in its air raids on Lebanon. In any event, the Hizbollah - which has carried out its assaults on Israeli military positions inside Lebanon - responded by promising Katyusha attacks across the border if Mr Kahalani fulfilled his promise. So the Israelis were trapped again, this time by their own threat.
They could, conceivably, leave the narrow finger of territory they still hold on the mountain chain to Jezzine; it might reduce their current casualty toll of 23 soldiers by about six or seven. But the Syrians - who want a retreat from Golan as well as southern Lebanon - are not going to force the Hizbollah to stop shooting just because Jezzine is returned to Lebanese authority.
The Israeli Prime Minister still says he wants to abide by UN Security Council Resolution 425 and withdraw; but 425 demands an immediate and unconditional withdrawal, and Benjamin Netanyahu wants to make lots of conditions - including the disarming of Hizbollah and the integration of Israel's SLA gunmen in the Lebanese army. "We saw what happened with the agreements Mr Netanyahu made with the Palestinians," a Lebanese diplomat said. "He just came up with more conditions. We're not going to play that game."
As for the Israelis, they are now so fearful of being blown up in their own tanks by roadside bombs that they are under orders to walk back to their country from their occupation zone - sometimes 10 miles at night and over rough country. Artillery bases needing 10 to 15 Israeli soldiers are now manned by scarcely half that number - even though three infantry brigades as well as armoured brigades are available in Israeli Brigadier General Gerstein's Lebanon Division. There is talk in the Israeli press of a collapse of morale in the army.
And rarely has such an accurate analysis as this been published on southern Lebanon: "Hizbollah has total control of the area; it is home to their fighters who are intimate with every clod of earth and every crevice. They initiate the moves and [the Israelis] only respond. When [Israel] initiates an offensive, the damage they suffer has no impact on the Hizbollah's fighting ability or spirit - because they are fighting an occupation."
Those extraordinary words of praise for the Hizbollah's guerrilla army were written just two days ago - by the Israeli journalist Yoel Marcus in the Israeli newspaper Maariv.