The conflict between Israel and Lebanon's Hezbollah is dangerously poised after more than eight months of fighting triggered by the Gaza war, with hostilities escalating and both sides signalling a readiness for a bigger confrontation.
The U.S. State Department said on Tuesday that Washington does not want to see a full-blown war and that it is trying to pursue a diplomatic solution, adding that Israel had the right to defend itself from the Iran-backed Hezbollah.
But political pressure is building in Israel for tougher action against the heavily armed group.
This is a primer on the conflict:
WHY ARE THEY FIGHTING?
Hezbollah, a Hamas ally, says its attacks aim to support Palestinians under Israeli bombardment in Gaza.
The violence is part of the regional spillover of the Gaza war, which has drawn in Iran-backed militants across the region. Hezbollah is widely deemed the most powerful member of the Iran-backed network, known as the Axis of Resistance.
While linked to Gaza, the conflict has its own dynamics.
Israel and Hezbollah have fought numerous wars.
The last was in 2006.
Israel has long viewed Hezbollah as the biggest threat at its borders and has been deeply alarmed by its growing arsenal, and the foothold it has established in Syria.
Hezbollah's ideology is largely defined by conflict with Israel. It was founded by Iran's Revolutionary Guards in 1982 to fight Israeli forces that had invaded Lebanon that year, and waged years of guerrilla war that led Israel to withdraw from south Lebanon in 2000.
Hezbollah deems Israel an illegitimate state established on occupied Palestinian lands and wants to see it gone.
WHAT'S THE IMPACT SO FAR?
The conflict has already taken a toll on both sides.
Tens of thousands of people have been forced to flee their homes on both sides of the border. Israeli airstrikes have pounded areas where Hezbollah operates in southern Lebanon and struck the Bekaa Valley near the Syrian border.
Israel has also occasionally hit elsewhere, notably killing a senior Hamas commander in Beirut on Jan. 2.
Israeli strikes have killed some 300 Hezbollah fighters in Lebanon - more than it lost in 2006, according to a Reuters tally. Around 80 civilians have been killed, according to a Reuters tally.
Attacks from Lebanon have killed 18 Israeli soldiers and 10 civilians, Israel says.
In Israel, the displacement of so many Israelis is a big political issue. Officials hope they will be able to go home for the school year beginning Sept. 1.
HOW MUCH WORSE COULD IT GET?
A lot. Despite the ferocity of these hostilities, this is still seen as a relatively contained confrontation.
Israeli Prime Minister Benjamin Netanyahu said on Wednesday Israel was prepared for strong action in the north. He warned in December that Beirut would be turned "into Gaza" if Hezbollah started an all-out war.
Hezbollah deputy leader Sheikh Naim Qassem signalled on Tuesday the group was not seeking to widen the conflict but he also said Hezbollah was ready to fight any war imposed on it.
In an interview with Al Jazeera, he said Hezbollah had used a small part of its capabilities. Any move by Israel to expand the conflict would be met by "devastation, destruction and displacement" in Israel, he said.
Past wars have inflicted heavy damage.
In 2006, Israeli strikes levelled large areas of Beirut's Hezbollah-controlled southern suburbs, knocked out Beirut airport, and hit roads, bridges and other infrastructure. Nearly 1 million people in Lebanon fled their homes.
In Israel, the impact included 300,000 people fleeing their homes to escape Hezbollah rockets and some 2,000 homes destroyed.
Hezbollah has a far bigger arsenal than in 2006, including rockets it says can hit all parts of Israel.
It has demonstrated advances in its weaponry since October, shooting down Israeli drones, launching its own explosive drones into Israel, and firing more sophisticated guided missiles.
Israeli troops have invaded Lebanon several times, reaching as far as Beirut in the 1982 invasion which aimed to crush Lebanon-based Palestinian guerrillas.
IS ESCALATION AVOIDABLE?
Washington and Paris have been seeking de-escalation.
"We've heard Israeli leaders say the solution that they prefer is a diplomatic solution. And obviously that is the solution that we prefer too and that we're trying to pursue," U.S. State Department spokesperson Matthew Miller said on Tuesday. The United States deems Hezbollah a terrorist group.
Hezbollah has signalled its eventual openness to an agreement that benefits Lebanon, but has said there can be no discussions until Israel halts the Gaza offensive - something mediators are struggling to achieve.
Israel has also indicated its openness to a diplomatic settlement that would restore security in the north, whilst preparing for a military offensive to achieve the same goal.
"Whoever thinks that they can harm us and we will sit idly by is making a big mistake," Netanyahu said on Wednesday. "In one way or another we will restore security to the north."
The U.S. official at the heart of diplomatic contacts, Amos Hochstein, brokered an unlikely diplomatic deal between Lebanon and Israel in 2022 over their disputed maritime boundary.
