What is Hezbollah, the group that poses threat to Israel from the north?

As Israel prepares a possible ground invasion of the Gaza Strip to destroy Hamas, the Palestinian militant group that controls the enclave, many are now turning to see what action Hezbollah, the armed group on Israel’s northern border, will take. For decades, Hezbollah has been a significant force in Lebanon, wielding both political power and military strength — all while engaging in tit-for-tat skirmishes with its southern enemy, Israel.

What is going on?

Israel and Hezbollah have been trading fire almost daily since Oct. 7, when Hamas mounted attacks in Israel that killed 1,400 people, according to Israeli authorities. With Israel threatening a ground invasion of the Gaza Strip, many in the region fear that the fighting with Hezbollah, an ally of Hamas, could escalate into a war involving Lebanon, too. This would leave Israel fighting on two fronts, a situation it wants to avoid.

Israel’s northern border has become increasingly tense: On Monday, the Israeli military said it would evacuate 28 communities near Lebanon, affecting about 10,000 people. At least three Lebanese civilians have died over the past week, including Reuters journalist Issam Abdallah. One Israeli civilian has been killed. A number of fighters from Hezbollah and Hamas also have been killed.

Mohamad Srour, the mayor of the Lebanese border town of Aita al-Shaab, has said Israeli bombings have struck homes, ambulances and a school for people with special needs, leading to injuries. At least 3,650 civilians displaced by the fighting have been registered in Tyre, a Lebanese city close to the border with Israel, and in recent days, U.N. peacekeeping forces in southern Lebanon have begun to shelter some civilians.

Where did Hezbollah come from?

The group traces its origins to a different ground invasion involving Palestinians. In 1982, Israel moved into southern Lebanon with the goal of quashing the Palestine Liberation Organization, or the PLO, whose leaders used the country as a base. Israel soon found itself up against a new Shiite-Muslim movement founded to rally popular will against the Israeli occupation. It took the name Hezbollah, Arabic for “Party of God.”

Hezbollah soon found a new ally in Iran, and a foe in the United States, after it was involved in the suicide bombing of the U.S. Embassy in Beirut in 1983. Israel withdrew from Lebanon in 2000, but Hezbollah’s threat has remained ever since.

Hamas has strengthened ties with Iran and Hezbollah in recent years following a period of colder relations a decade ago, when the two armed groups backed opposing sides in the Syrian civil war.

Has Hezbollah fought Israel before?

Yes. In 2006, the group fought a bloody war that lasted 34 days and left sections of Beirut, and other parts of Lebanon, leveled by Israeli airstrikes. At least 1,109 Lebanese citizens died, according to Human Rights Watch, along with scores of Israeli soldiers and Hezbollah fighters. The war also started at the northern border: That July, a Hezbollah raid into Israel killed eight soldiers and kidnapped two others. The violence quickly escalated from there.

Is Hezbollah popular in Lebanon?

Hezbollah and its political allies lost their majority in Lebanon’s parliament in elections last year, but the group remains a formidable political force that continues to exercise de facto control over parts of the country, including southern Lebanon.

It has led to Hezbollah’s reputation as a state within a state, with an expansive security apparatus and social services network that have largely weathered the economic crisis that has befallen the country.

This article originally appeared in The New York Times.