Israel’s military carried out a massive exercise this month simulating a conflict with Hezbollah, the largest drill in nearly two decades. (Jalaa Marey/Agence France-Presse/Getty Images)

Israel has flexed its military muscles in recent months as the regional balance of power has pitched further in favor of its most bitter adversaries: Iran and its Lebanese proxy, Hezbollah.

Analysts and former senior Israeli military officers say Israel is showing that it will act with force to protect its interests, while using just enough of it to limit its enemies without sparking a war. But it’s a precarious line to tread, and even a small misstep could lead to conflict, they say.

Israel is scrambling to adjust as Syrian President Bashar al-Assad has taken the upper hand in his country’s six-year war, propped up by an emboldened Iran and an array of Shiite militias, including Hezbollah, which has sent thousands of fighters to back him.

The Israeli government had expressed frustration as the Trump administration focused on fighting Islamic State militants without, in Israel’s opinion, sufficiently limiting Iran and its proxies. Israeli Prime Minister Benjamin Netanyahu publicly criticized a U.S.-Russia cease-fire deal in southern Syria for not including provisions to stop Iranian expansion.

Israel is now making itself heard. Last week, Israeli jets buzzed so low over southern Lebanon that they shattered windows and caused panic. That followed this month's bombing of a military site in Syria that had been linked to missile production for Hezbollah.

On Tuesday, the army used a Patriot missile to shoot down a drone that neared its airspace.

Threats have escalated on both sides. “If the Zionist regime makes any wrong move, Haifa and Tel Aviv will be razed,” Iran’s army chief, Maj. Gen. Abdolrahim Mousavi, warned this week in comments published by the semiofficial Fars News Agency, referring to Israeli cities within the range of Hezbollah rockets.

Hezbollah and Israel fought a month-long war in 2006 that caused heavy casualties, and both sides claimed victory. Since then, the Syrian war has provided Hezbollah fighters with a training opportunity, while Israel estimates that the militia has built up a stockpile of more than 100,000 rockets.

Israel fears that Iran will help Hezbollah upgrade to more accurate precision-guided missiles and establish a permanent military presence in Syria, from where the militia could eventually turn its focus south.

“Generally speaking, this is the kind of threat we can’t live with,” said Brig. Gen. Nitzan Nuriel, a former Israel Defense Forces officer who was deputy commander of the division responsible for the Lebanese front during the 2006 war. “This is the kind of threat we need to deal with.”

In recent months, Netanyahu has accused Iran of establishing manufacturing sites for long-range missiles in both Lebanon and Syria. Satellite images showing one alleged site, near the Syrian port city of Baniyas, were shared with the news media.

Israel seeks to leverage more favorable outcomes in Syrian cease-fire deals where it feels its interests have been ignored, and public threats and messages are meant as much for Israel's allies as its enemies, Nuriel said.

“At the same time, we will try to keep Hezbollah weak to remind them what happened in 2006,” he said.

After speaking out against the “deescalation” deal for southern Syria reached by the United States and Russia on the sidelines of the Group of 20 summit, Netanyahu traveled to Sochi to meet with Russian President Vladimir Putin. A high-level delegation was also dispatched to Washington.

Russia’s foreign minister, Sergei Lavrov, later made a public assurance that Israel’s security interests in southern Syria were being taken into account.

In a speech last month, Hezbollah's secretary general, Hasan Nasrallah, mocked Netanyahu for "crying" over the defeat of the Islamic State in Iraq and Syria.

Nasrallah has repeatedly warned Israel against attacking Lebanon.

“If the Israelis think they can now make war in Lebanon, then they are making a big mistake. In Syria, we have learned to attack,” said a senior official from the military alliance of Hezbollah, Syria and Iran. He spoke on the condition of anonymity because he is not authorized to speak with the news media.

“The rhetoric on both sides is a substitute for action — a way of reinforcing deterrence without having to take military action — and a way of saving face,” said Faysal Itani, a fellow at the Washington-based Atlantic Council. “But I do think things are trending negatively.”

Netanyahu tried to drive home his point Tuesday at the U.N. General Assembly in New York, saying that “those who threaten us with annihilation put themselves in mortal peril.” Israel will act to prevent Iran from opening “new terror fronts” on Israel’s northern border, he said.

He also pushed for changes to the international deal limiting Iran’s nuclear activities.

Israeli Prime Minister Benjamin Netanyahu addresses the 72nd session of the General Assembly at the United Nations in New York on Sept. 19. (Jewel Samad/Agence France-Presse/Getty Images)

“This is all classic Netanyahu,” said Ofer Zalzberg, a senior analyst at the International Crisis Group. “Saying, ‘Hold me back before I do something.’ But I don’t see Israel launching a preemptive war. The next war between Israel and Hezbollah will be dramatic for Israel’s population and will have consequences for whoever is in power.”

But the prospect is not impossible; there are some Israeli officials advocating intervention, he said, describing Israel as “panicked.” “Advocates are saying bomb now.”

They see a window of opportunity. While Syria has refrained from retaliating against Israeli strikes on its soil, that is likely to change as the war draws to an end, raising the stakes of the occasional intervention with airstrikes that Israel is currently engaged in.

In Lebanon, Hezbollah’s growing strength has come at a cost, one that could cause personnel problems in the event of renewed conflict.

The group does not publish figures for the number of its members who have fought and died in Syria, but more than 1,000 have been killed, according to one study of Arabic language news coverage of funerals in Lebanon.

On a recent day in the Beirut suburb of Dahiyeh, a steady trickle of relatives passed through a newly opened cemetery for fighters killed recently in Syria. Marble slabs are adorned with photographs of the men in fatigues, some decorated with roses for Father’s Day.

Sitting quietly at the gravestone of a commander killed last year, a woman named Rukiya said her son died in the battle to recapture the northern city of Aleppo. “He knew he didn’t have to go, but he didn’t listen to me,” she said. “The resistance was everything to him.”

But in the war, Hezbollah has also gained experience. The Israeli military now fears a scenario in which Hezbollah, which formed in the 1980s to fight the Israeli occupation of Lebanon, could raid one of Israel’s 22 border communities as war in Syria winds down.

In April, Hezbollah organized a rare trip for journalists to the area to highlight what appeared to be newly constructed fortifications on the Israeli side of the U.N.-patrolled buffer zone between the two countries.

“The Israeli enemy is undertaking these fortifications and building these obstacles in fear of an advance,” said a Hezbollah commander who went by the nom de guerre Haj Ihab.

Israel’s Defense Ministry confirmed that it was indeed bolstering its defenses, including walls near northern communities that are vulnerable to cross-border sniper fire or antitank missiles, Israeli media reported. It also said the project will cost about $34.7 million.

“We are strengthening the border based on the understanding that in any future conflict, Hezbollah would make a concerted effort to cross the border,” said an Israel Defense Forces official in the Northern Command who spoke on the condition of anonymity because he was not authorized to talk publicly.

In the meantime, Israel will continue its strategy of “deterrence and prevention,” Nuriel said, managing the risks of escalation.

“You need to ask yourself, if you do this, what will the enemy do?” he said. “Many times we decide taking action is better.”

But Israel’s 2006 war with Hezbollah began when militants launched a cross-border raid on an Israeli patrol, killing three Israeli soldiers and capturing two. Nasrallah later said that if he’d known how Israel would react, Hezbollah would not have carried out the raid. The war left 1,000 Lebanese and nearly 160 Israelis dead. Now the stakes are higher.

“Syria made the machine faster,” said Kamal Wazne, a professor at the American University of Beirut who studies the group. “A confrontation is going to be deadly, destructive and painful for both sides.”

Loveluck reported from Beirut. Ruth Eglash in Jerusalem and Suzan Haidamous in Beirut contributed to this report.

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