On a recent night, three guerrillas infiltrated into Israel. They moved stealthily, but their every footstep was captured by real-time video monitors in a secret Israeli border observation post.
Without warning, Israeli mortar shells flashed across the video console; two of the interlopers were killed. A third "played dead." After a few minutes, he got up and ran. Another mortar flashed across the screen, and the night was quiet again.
This has long been one of the world's most closely monitored borders.
Now it is being watched with growing alarm that a new Arab-Israeli conflict is about to break out, fanning the Israeli-Palestinian conflict to the south into a region-wide war.
The Islamic group Hezbollah, which controls much of southern Lebanon and receives backing from Syria and Iran, has begun launching daily fusillades of Katyusha rockets and antitank rounds into Israel. On Friday, Hezbollah fighters attacked Israeli positions and Israel retaliated, using its warplanes, helicopters and artillery to attack near the border in southern Lebanon.
Hezbollah's apparent aim is to trigger a massive Israeli response and open a "second front" _ the first being on the West Bank and Gaza Strip _ in the Arab-Israeli conflict.
"Over here, it can very easily develop into a wider war," said Maj. Dinor Shavit, spokesman for the Israel Defense Forces' Northern Command, as he conducted a tour of the tense border region.
For both the United States and Israeli Prime Minister Ariel Sharon, the conflict presents a dilemma.
Even if President Bush and Secretary of State Colin Powell succeed in returning Israelis and Palestinians to the peace table, their work in the Middle East will be far from done.
For Sharon, who spearheaded Israel's invasion of Lebanon 20 years ago to oust Palestinian guerrillas, the attacks by Hezbollah are difficult to ignore, even if the inaccurate Katyushas only occasionally cause damage.
So far, Israel has responded in kind when attacked, launching artillery and airstrikes. Soldiers have standing orders not to fire unless intruders cross the international border, known as the "Blue Line."
But if the attacks continue, officials warn, there could be a disproportionate response, aimed not at Hezbollah but at its backer Syria, the dominant power in Lebanon.
"Syria is the key player here. They are the ones who control the amount of violence," Shavit said. If you are bitten by a dog, "you don't go after the dog. You go after the owner," he said.
Israel has warned Syria to desist, in messages passed via the United Nations and the European Union, and echoed by the United States.
Friday was a typically tense day along the far northern border, a land of mountains and lush green pastures framed on the east by snow-capped Mount Hermon and to the north and west by Lebanese territory under Hezbollah control.
First, word crackled across the radio that two men were preparing to infiltrate from Lebanon across a net of fences, listening posts and observation balloons that Israel has erected since it withdrew from Lebanon nearly two years ago.
Then, at an army post in the middle of the kibbutz Misgav Am, antiaircraft fire boomed from the Lebanese side of the border. Israeli soldiers, after scrambling in and out of bunkers, tried to pinpoint the source of the fire.
Later, Hezbollah launched six Katyusha rockets and a mortar shell at Israeli military posts in the Chebaa Farms area between Lebanon, Israel and the Israeli-occupied Golan Heights. Hezbollah contends that the area is part of Lebanon, although the United Nations confirmed two years ago that Israel had withdrawn from all Lebanese territory.
The rocketing and shelling, at first confined to Chebaa Farms, has since spread. Last month, guerrillas found a weak point in the fence and crossed, killing six Israelis, including one soldier, before being killed themselves.
At the secret observation post, where all the soldiers staffing the dozen or so consoles are women, videotape of the antiaircraft fire is rewound and played for visitors.
"If they're not going to stop this, definitely it's very dangerous," said Gadi, commander of intelligence collection for the area, who asked that only his first name be used. It "can lead to fighting and the fighting can lead to a war."
Hezbollah, which means Party of God, was formed in response to Israel's 1982 invasion and has Shiite Muslims in southern Lebanon as its support base. Led by Hassan Nasrallah, it espouses a radical form of Islam imported from Iran. Arms come from Tehran and training takes place in the Syrian-controlled Bekaa Valley of Lebanon.
When Israel withdrew its troops from Lebanon, it was Hezbollah, not the weak central Lebanese government, that took control over the south of the country.
Within feet of an Israeli observation post, yellow Hezbollah flags fly and the group has erected a large signboard with ghastly pictures of dead and mutilated Israeli soldiers from the earlier war. Underneath is the slogan: "Sharon: Don't Forget Your Soldiers Still in Lebanon."
Most observers believe that Lebanese Prime Minister Rafik Hariri is more interested in rebuilding his country, still suffering from the effects of a 25-year civil war, than engaging Israel. But he may be powerless to restrain Hezbollah.
Syria's motivations are harder to divine, although President Bashar Assad may see Hezbollah as a useful tool to harass Israel while avoiding a full-scale conflict with the superior Israeli military.
Israel's generals and politicians seem torn, leery of a new battlefield, but unwilling to show restraint indefinitely.
"We don't want to get into Lebanon" again, Shavit said. "But we can't sit quietly if it continues."