NABATIYEH, Lebanon: Israel's "security zone" in southern Lebanon has turned into a war zone once again. Hezbollah guerrillas and the Israeli army have been trading deadly blows since Thursday, when a clash resulted in the death of one of the guerrillas. At 5:30 a.m. Friday, local time, Hezbollah responded by peppering an Israeli-occupied border enclave in the zone with machine-gun fire and mortar shells, killing one Israeli soldier and wounded three others, according to Israeli security officials. Israel gunners retaliated with three hours of heavy artillery fire on suspected guerrilla hideouts in the vicinity of villages facing Israeli positions in the enclave, the officials said. And Israeli warplanes, backing up the shelling, raided suspected Hezbollah positions this morning in an area near Nabatiyeh. There were no reported injuries. "Sadly, there is nothing unusual at all about this," says TIME's Bill Stewart. "This will continue periodically until Israel finds a way to extricate itself from Southern Lebanon." The exchange, says Stewart, accomplished exactly what Hezbollah wants: to keep the conflict alive and the pressure on Israel. Calls continue in Israel for a troop withdrawal from the zone. But most in the Israeli government, and indeed in the United States', feel that Israel's troops are where they must be. "The purpose of the zone is actually not to prevent conflict," says Stewart, "but to prevent conflict from occurring on Israel soil." Pulling out now, he says, would only serve to move the 'front' south, to Israel's northern border. And the troop presence remains Israel's most valuable card in any negotiations with Syria. Until such talks get under way, Stewart says, expect the ongoing conflict to continue. And the soldiers to keep dying.