The 1982 Lebanon war began on 6 June 1982, when Israel invaded again for the purpose of attacking the Palestine Liberation Organization. The Israeli army laid siege to Beirut. During the conflict, according to Lebanese sources, between 15,000 and 20,000 people were killed, mostly civilians.

On 16 February 1985, Shia Sheik Ibrahim al-Amin declared a manifesto in Lebanon, announcing a resistance movement called Hezbollah, whose goals included combating the Israeli occupation. During the South Lebanon conflict (1985–2000) the Hezbollah militia waged a guerrilla campaign against Israeli forces occupying Southern Lebanon and their South Lebanon Army proxies.

• https://en.wikipedia.org/wiki/Israeli–Lebanese_conflict

Throughout the painstaking process of confirming the Israeli withdrawal, Hizballah was at pains to declare its commitment to recovering the last millimeter of Lebanese territory, but it also acknowledged that it would not act hastily to reinitiate violence. In sum, Hizballah’s behavior and deference to state authority have worked to its political advantage. It reaped recognition in an unprecedented meeting between Nasrallah and UN Secretary-General Kofi Annan, who praised Hizballah’s restraint and its promise of cooperation. The meeting with Annan offers a remarkable contrast with Hizballah’s earlier days, when it was hostile to the UN and especially to the UN force in the south.

Without an agreement between Syria and Israel, there will be little pressure on Hizballah to disarm. Syria’s calculated strategy is to allow Hizballah to serve as a constant reminder of the consequences of continuing to occupy the Golan Heights.This is a role that Hizballah is happy to play, given its enmity toward Israel. At the same time, it remains profoundly aware of the political costs of bringing destruction down on the heads of its supporters, and this further reduces the prospect that Hizballah will initiate attacks on Israel

• https://sci-hub.se/https://doi.org/10.2307/2676479

The doctrine is named after the Dahiya suburb of Beirut, where the Lebanese paramilitary group Hezbollah has its headquarters, which the Israeli military leveled during its assault on Lebanon in the summer of 2006 that killed nearly 1,000 civilians, about a third of them children, and caused enormous damage to the country’s civilian infrastructure, including power plants, sewage treatment plants, bridges, and port facilities.

It was formulated by then-General Gadi Eisenkot when he was Chief of Northern Command. As he explained in 2008 referring to a future war on Lebanon: "What happened in the Dahiya quarter of Beirut in 2006 will happen in every village from which Israel is fired on… We will apply disproportionate force on it (village) and cause great damage and destruction there. From our standpoint, these are not civilian villages, they are military bases… This is not a recommendation. This is a plan. And it has been approved.” Eisenkot went on to become chief of the general staff of the Israeli military before retiring in 2019.

While it became official Israeli military doctrine after Israel’s 2006 attack on Lebanon, Israel’s military has used disproportionate force and targeted Palestinian, Lebanese, and other civilians since Israel was established in 1948 based on the ethnic cleansing of indigenous Palestinians, including dozens of massacres to force them to flee for their lives.

• The Dahiya Doctrine & Israel’s Use of Disproportionate Force

Until recently, the border had been relatively quiet. Occasional rockets or drones crossed from Lebanon into Israel without leading to serious escalation, while Israel violated Lebanese airspace more than 22,000 times from 2007 to 2022.

• https://www.aljazeera.com/news/2023/10/17/beyond-hezbollah-the-history-of-tensions-between-lebanon-and-israel

• https://en.m.wikipedia.org/wiki/Israeli–Lebanese_conflict

While the withdrawal was certified by the United Nations, Lebanon disputed it, arguing that the Shebaa Farms was part of its territory, and not part of the Syrian Golan Heights, which Israel continues to occupy.

So there are two separate issues here that lead to the current dispute: the first is that Israel occupies the Golan Heights and treats it as its own territory in violation of international law, and the second is that there was already a pre-existing disagreement between Syria and Lebanon over the border, prior to the Israeli occupation.

• https://www.aljazeera.com/news/2023/7/13/why-is-there-a-disputed-border-between-lebanon-and-israel