For months, concerns have grown that the war in Gaza might ignite a second conflict between Israel and Hezbollah, the well-armed militia that is loosely allied with Hamas and based just across Israel’s northern border with Lebanon.

The two sides have repeatedly traded strikes since the Gaza war began in October, killing civilians and combatants in Lebanon and Israel, with most of the civilian casualties in Lebanon. The hostilities have also forced more than 150,000 people on both sides of the border to leave their homes for temporary shelters. That has put pressure on the Israeli government to make the north of the country safe for residents again by pushing Hezbollah back from the border region.

The pagers that exploded across Lebanon on Tuesday came a day after Israeli leaders warned that they were considering stepping up their military campaign against Hezbollah. Israel hasn’t commented on whether it was behind the attacks, but tensions between the two countries were already rising.

Here’s a look at Hezbollah and what a wider war would mean for Lebanon.

What is Hezbollah?

Hezbollah has opposed Israel since the group’s very beginnings. It was founded in the 1980s, after Israel, responding to attacks, invaded and occupied southern Lebanon, intending to root out the Palestine Liberation Organization, which was then based in the country.

But Israel soon ran into a new enemy, one whose guerrilla fighters quickly grew effective at bedeviling the far-better-equipped Israeli forces: Hezbollah, a Shiite Muslim popular movement that made driving Israel out of Lebanon a major goal.

By 2000, Israel had withdrawn from Lebanon, making Hezbollah a hero to many Lebanese. It fought Israel again in 2006, launching a military operation into its southern neighbor that led to a fierce counterattack. In that war, Israel rained bombs on southern Lebanon and Beirut, the capital; the fighting killed more than 1,000 Lebanese.