What is Hezbollah and what does Lebanon have to do with the Israel-Hamas war?
Thousands of people were injured and at least nine killed in Lebanon and Syria on Sept. 17 when pagers held by members of the Iran-backed group Hezbollah, a powerful ally of Hamas, exploded almost simultaneously in their hands, bags and pockets. Hezbollah and Lebanese officials quickly blamed Israel for what appeared to have been a well orchestrated attack.
Hezbollah vowed to exact revenge, further fueling concern of a possible full-scale war between the group and Israel, as the war between Israel and Hamas continues in Gaza.
Israel's government and military declined to comment on the explosions, but The Associated Press said Israeli officials had briefed the U.S. government on the operation retrospectively. Pentagon Press Secretary Major General Patrick Ryder said earlier that the U.S. had no involvement in the attack.
"It's a warning," Sima Shine, the former head of research at Israel's foreign intelligence agency Mossad, told CBS News. "If Israel did it, it has to take into account that Hezbollah will retaliate, and we are escalating to a kind of a war — short, long, I don't know — but a war."
Below is a look at what's going on, the background to the long-simmering tension between Israel and Hezbollah, and the risks for the region and the world.
What's happening now along the Lebanon-Israel border?
U.S. officials have pushed Israel for months to contain its engagement with Hezbollah to avoid igniting a wider regional conflict that could put American forces across the Middle East in direct danger. Ryder stressed after the pager explosions that the Pentagon still considered diplomacy "the best way to reduce the tensions along the Israel-Lebanon border."
Almost daily since the Israel-Hamas war began, Hezbollah rockets have struck Israeli positions, including military posts, in northern Israel. Israel has also hit targets in southern Lebanon, and tens of thousands of people from border communities in both countries have been evacuated.
Israel has vowed for weeks to end the cross-border rocket fire, and senior Israeli officials have said recently that they believe military force is the only way to achieve that goal.
The country's security cabinet had already authorized Prime Minister Benjamin Netanyahu and Defense Minister Yoav Gallant to determine how and when to retaliate for a deadly July 27 rocket strike that hit a soccer field in the Israeli-controlled Golan Heights, killing at least 12 young people. Israeli and U.S. officials blamed the strike on Hezbollah, though the group issued a rare, categorical denial of any involvement in the attack.
Ryder said at the Pentagon after the pager explosions that the U.S. military was "not tracking anything in terms of ground incursions at the moment," but he left it to the Israeli military "to talk about their operations."
What is Hezbollah?
Modern-day Lebanon was founded in 1920 under a sectarian system that saw official government positions shared out among a number of recognized religious sects in the country.
The militant group Hezbollah was formed in 1982 as a Shiite Muslim political and military force, with the support of Iran and Syria, after an Israeli invasion of Lebanon. It functions within the Lebanese government as a political party, but also outside of it, providing services to its Shiite followers and maintaining its own paramilitary force.
While not a recognized military, Hezbollah's top leader, Hassan Nasrallah, said last year that the group had some 100,000 fighters at its disposal, and it is believed to be a better equipped, larger fighting force than Lebanon's actual state military.
Like its much smaller Iran-backed ally Hamas, Hezbollah has been designated a terrorist organization by the United States government for almost two decades, and several of its leaders, including Nasrallah, are listed as global terrorists.
What does Lebanon have to do with the Israel-Hamas war?
Lebanon is a country of about 5.3 million people just to the north of Israel. The two nations have fought multiple wars.
When the state of Israel was established in 1948, more than 100,000 Palestinian refugees fled to Lebanon. UNRWA, the United Nations aid agency for Palestinians, says there are currently between 200,000 and 250,000 Palestinian refugees living in Lebanon, many of whom it says live in poverty due to "decades of structural discrimination related to employment opportunities and denial of the right to own property."
After Israel responded to Hamas' Oct. 7 terror attack by launching the war in Gaza, with the stated objective of destroying the group, Hezbollah started attacking targets in northern Israel, in support, it says, of Hamas and the Palestinian people.
Hezbollah has said it did not know the Oct. 7 attack was coming ahead of time, and it is not believed to coordinate extensively with Hamas.
Iran's "resistance front" and the prospect of a wider war
Iran supports both Hezbollah and Hamas, as well as the Houthi rebel movement in Yemen that has been attacking ships in the Red Sea, severely impacting maritime trade through the vital shipping passage.
All of the Iran-backed proxy groups operating in the region have said their actions are in support of the Palestinian people, and none of them acknowledge any orchestration or coordination with Iran, which denies any role in the attacks.
"There is, as Iran calls it, a resistance front, that everybody will support Hamas [in its fight against Israel], that it will be not only supported with arms but also with money, and will be supported diplomatically," Shine, the former Mossad researcher who's now the head of the Iran program at the Institute for National Security Studies, told CBS News earlier this year.
Shine said Hezbollah likely doesn't want to engage in a war directly with Israel, in part due to the chaotic domestic political situation in Lebanon — a state she describes as "really on the verge of bankruptcy."
"The anti-Hezbollah motivation within Lebanon, and the fear of escalating the situation in Lebanon into a more difficult economic situation… I think this is also a very important reason" for the group to try to avert a full-scale war, Shine said.
But Hezbollah holds so much power inside Lebanon that the nation's wider government likely has little scope to decide whether a war with Israel is fought or not. That decision lies ultimately with Hezbollah's leaders — and their sponsors in Iran.