Israel and Hezbollah have traded fire across the Lebanese border since the start of the war in Gaza, with more than 150,000 people on both sides of the boundary forced to flee their homes. But the intensity of the attacks has increased in recent days, leading to fears of a full-scale war on another front.

This week, Prime Minister Benjamin Netanyahu of Israel threatened further military action to ensure the return of civilians to communities in northern Israel. Here are some key questions about the conflict and where it might be heading:

Why are the two sides fighting?

Hezbollah, a powerful Lebanese militia and political movement, launched attacks into Israel on Oct. 8, answering calls by Hamas to open a second front a day after the Palestinian armed group that rules Gaza led a deadly assault on Israel. Both Hezbollah and Hamas are backed by Iran.

Hezbollah’s leader, Hassan Nasrallah, has said that his group is trying to pin Israel’s troops along the border and limit its capacity to attack Hamas in Gaza.

Hezbollah’s conflict with Israel goes back decades. Israel has invaded Lebanon three times in the last 50 years, most recently in 2006, when the two sides fought a monthlong war that killed more than 1,000 people in Lebanon, mostly civilians, and more than 150 in Israel, mostly soldiers. The current round of fighting marks the most serious escalation since then.

What is the latest?

Israel in February launched its deepest strikes into Lebanon in years, hitting the Bekaa Valley in response to a surface-to-air missile attack that downed an Israeli drone over southern Lebanon.