Eli Harel was an Israeli soldier in his early 30s when he was sent to Lebanon in 2006 to battle terrorists from the Iranian-backed Hezbollah in a bloody, largely inconclusive month-long war.

Now 50, Harel is ready to rejoin the army to fight the same terror group if shelling along Israel’s northern border turns into a full-blown war with Iran’s most powerful regional proxy. This time, Israeli forces would face some of the most challenging fighting conditions imaginable, he said.

“There are booby traps everywhere,” he told Reuters. “People are popping up from tunnels. You have to be constantly on alert — otherwise you will be dead.”

Harel lives in Haifa, Israel’s third biggest city, well within range of Hezbollah’s weapons. Haifa’s mayor recently urged residents to stockpile food and medicine because of the growing risk of all-out war.

Israel and Hezbollah have been engaged in escalating daily cross-border strikes over the past six months — in parallel with the war in Gaza — and their increasing range and sophistication has spurred fears of a wider regional conflict.

Hezbollah has amassed a formidable arsenal since 2006.

Like Hamas, the terror group battling Israel in Gaza, Hezbollah has a network of tunnels to move fighters and weapons around. Its fighters have also been training for more than a decade with Syrian President Bashar al-Assad’s forces.

Hezbollah has so far restricted its attacks to a strip of northern Israel, seeking to draw Israeli forces away from Gaza. Israel has said it is ready to push Hezbollah back from the border, but it is unclear how.

Some 60,000 residents have had to leave their homes in the first mass evacuation of northern Israel, and cannot safely return, prompting increased calls within Israel for firmer military action against Hezbollah. Across the border in Lebanon, some 90,000 people have also been displaced by Israeli strikes.

Eyal Hulata, a former Israeli national security adviser, said Israel should announce a date in the next few months when displaced Israeli civilians can return, effectively challenging Hezbollah to scale back its shelling or face all-out war.

“Israelis cannot be in exile in their own country. This cannot happen. It is the responsibility of the IDF to defend civilians. It is what we failed to do on October 7,” he said, referring to the Hamas massacre of southern communities that prompted the current war in Gaza

Hezbollah did not respond to a request for comment. The group’s leader Sayyed Hassan Nasrallah said in February that residents of northern Israel “will not return” to their homes.

The Israeli military said this month that it had completed another step in preparing for a possible war with Hezbollah that centered on logistics, including preparations for a “broad mobilization” of reservists.

A conflict between Israel and Hezbollah would probably result in massive destruction in both countries. In the 2006 war, 1,200 people in Lebanon were killed and 158 in Israel.

So far, the skirmishes on the border have resulted in nine civilian deaths on the Israeli side, as well as the deaths of 11 IDF soldiers and reservists. There have also been several attacks from Syria, without any injuries.

Hezbollah has named 289 members who have been killed by Israel during the ongoing skirmishes, mostly in Lebanon but some also in Syria. In Lebanon, another 56 operatives from other terror groups, a Lebanese soldier, and at least 60 civilians, three of whom were journalists, have been killed.

If war did break out, Israel would probably bomb targets in southern Lebanon before soldiers tried to push at least 10 kilometers (6.2 miles) across the border. Hezbollah would likely use its estimated arsenal of over 150,000 rockets to target Israeli cities. In 2006, the group fired about 4,000 missiles at Israel.

Assaf Orion, a retired Israeli brigadier general, told Reuters there was a growing likelihood of war erupting between Israel and Hezbollah, caused either by an unplanned escalation in clashes or by Israel losing patience with people being unable to return home.

Orion said the intensity of bombing in any war could be 10 times greater than in Gaza.

“The damage will be immense,” he said. “Gaza will look like a walk in the park compared to that level of fighting.”

Haifa, a port city built on the slope of a mountain from where it is possible to see the Lebanon border on a clear day, was targeted in 2006. Eight people were killed in the worst attack.

Nasrallah said in 2016 that Hezbollah could hit ammonia storage tanks in Haifa, saying the result would be “like a nuclear bomb.”

The mood in Haifa is a mixture of anxiety and fatalism.

Hundreds of evacuated Israelis have moved to the city and many said another war may be the only way to return home.

Assaf Hessed, 35, who lived in a kibbutz two kilometers (1.2 miles) from the border, said the military has until September to force Hezbollah back or residents will move elsewhere.

“We have to make a decision soon about where we live, we cannot go on like this much longer,” he said.