Israel’s recent invasion of Lebanon may have come after months of trading fire with its longtime Lebanese enemy Hezbollah, but the conflict between the two countries goes back decades — before Hezbollah even existed.

At the center of the hostilities between the two countries is the issue of Palestine. Israel’s friction with Lebanon began when the latter absorbed more than 100,000 Palestinian refugees in the wake of Israel’s founding in 1948. That friction has only intensified in the decades since, as those refugees, their descendants, and the Lebanese groups they inspired agitated for various forms of self-determination.

Israel launched the current invasion into southern Lebanon on October 1, to push Hezbollah, an Iran-aligned Shia militant and political group, back from its positions in southern Lebanon. Israel hoped to send tens of thousands of its citizens back to their homes in the country’s north, a year after they were forced to leave due to Hezbollah rocket fire.

Throughout the war, Hezbollah has said that it will not cease attacks on Israel until there is a ceasefire in Gaza, though the group’s leadership recently endorsed ceasefire talks that didn’t hinge on a Gaza truce. More than 42,000 Palestinians have been killed in Gaza over the past year by the Israeli military’s ongoing operations.

The costs of the invasion are quickly rising. Israel has displaced the inhabitants of dozens of villages in southern Lebanon — more than 1 million people, in a population of 6 million — and repeatedly bombed the capitol, Beirut, and its southern suburbs. More than 2,000 Lebanese have been killed in the past year, most in the past month. Over the past year, 28 Israeli civilians and 43 Israeli soldiers have been killed by Hezbollah attacks and in recent ground operations.

Though Israel initially promised a “limited” operation in Lebanon, US officials have warned the Israelis about “mission creep” there as the fighting stretches on. And Israel’s decision to invade has also renewed fears of a wider war, especially given the escalation between Israel and Iran. That said, to fully understand what’s happening in Lebanon right now, we’ll need to go back decades. Here’s a timeline of the fraught Israel-Lebanon relationship that can help explain how we arrived at the current situation.

Before there was the state of Israel, there was the Zionist settler colonial project, started in the 19th century by European Jews hoping to create a homeland and escape the pogroms and persecution they faced for centuries in European countries. (Arab Jewish communities had lived for centuries throughout the Middle East, often in cooperation with neighbors of other religions, but with their own distinct culture.)

European Jews began settling in Palestine in the late 19th century. At that time, Lebanon was overseen by France, and Palestine by Britain. As more European Jews began settling in Palestine in the face of rising fascism and antisemitic violence on the continent, Zionists appealed to European powers for a Jewish state in Palestine.

In 1947, the United Nations granted that appeal, calling for a partitioned state of Palestine. By that time tensions between Jewish communities and the Muslim countries they lived in were rising, as leaders of Arab countries associated those communities to Zionism; that led to the expulsion of many Jewish communities across the region. Jewish militias had also ethnically cleansed many Palestinian villages and towns; in response to this violence and in defiance of another European colonial project, a full-scale war, known as the Arab-Israeli War, broke out in 1948.

Lebanon was one of the group of allied nations fighting the newly formed Israel and was a safe harbor for some of the 750,000 to 1 million Palestinians forced to flee their homes during the war, an event referred to as the Nakba.

Lebanon mostly welcomed the Palestinian refugees, understanding their status to be temporary. But Lebanon’s political system divides power among the nation’s religious groups, and the influx of mostly Sunni Muslim Palestinians threatened to upset the country’s fragile sectarian power-sharing dynamic. The Lebanese government operates on a confessional system, meaning political power is accorded to different religious groups based on population. That gave the Maronites — a Catholic sect exclusive to Lebanon — significant political power.

Since then, Muslim Palestinians have been relegated to second-class status in Lebanon while Christians were able to gain citizenship. This dynamic would, over the decades, resonate with disenfranchised Lebanese from other religious groups, feeding both internal conflict and conflict with Israel.

The Arab-Israeli War also upended the economic stability of southern Lebanon, in a way the area never really recovered from. Prior to 1948, many people in southern towns and border villages relied on access to Palestinian cities for their livelihoods. They lost that access once the state of Israel was formed, and movement was further restricted after the war — Israel captured and incorporated a number of southern Lebanese villages.

Following the Nakba, Lebanon’s government sought to avoid the ongoing Arab-Israeli conflict, given its weak military and the economic support it was enjoying from the US.

However, a war in 1967 — known as the Six-Day War — thrust Lebanon back into the conflict.

The war’s precipitating events began in 1965, when Palestinian groups based in Lebanon, Jordan, and Syria began launching attacks on Israel, against which the Israeli military retaliated with immense force. Those tit-for-tat strikes continued for two years, until Egypt entered the fray.

In response to false reports that Israel was scaling up forces on the Syrian border, Egypt mobilized troops, kicked out UN peacekeepers, and closed a key strait, effectively blockading Israel. Syria, Jordan, and Iraq allied themselves with Egypt. Israel then launched a preemptive strike that destroyed most of the Egyptian Air Force, and quickly defeated Egypt and its allies, capturing and claiming new territory: the Sinai Peninsula and Gaza from Egypt, the Golan Heights from Syria, and the West Bank and Jerusalem from Jordan.

All of this has two things to do with Lebanon.

One, the defeat of these allied Arab national armies dealt a death blow to the pan-Arab movement, which was supposed to liberate Palestine. In the immediate term, that meant the Palestinians displaced in the Nakba — including all those living in Lebanon — weren’t going back to their homes any time soon.

Two, that reality meant Palestinian militant groups understood they had to fight for their own national liberation.

Those groups — and their message — proliferated in the years following the war. Many, most notably the Palestine Liberation Organization, the national liberation and militia group headed by Yasser Arafat, made Beirut their headquarters.

From Lebanon, those groups would continue to stage attacks targeting Israel.

Before Palestinian militias in Lebanon became models for groups like Hezbollah, they were the inspiration for — and later, partner to — various left-wing armed Lebanese groups disenfranchised by the country’s political structure.

Again, Lebanon’s government is run under what is called a confessional system, in which political representation is based on religion. The president has always been a member of Lebanon’s Maronite Christian group, and the prime minister a Sunni Muslim, with lesser positions and representation for the country’s other religions like the Druze, Shia Muslims, and other Christian sects. Though presidential powers and parliamentary representation have changed, the system remains largely intact. It also reflects significant class divides.

Palestinians arriving in Lebanon during the Nakba were largely Muslims (though some belonged to the Greek Orthodox faith). That influx of Muslims into tiny Lebanon upset the sectarian balance of power — something that would have long-term consequences.

“As a result of Palestinian presence in Lebanon, you have a situation where old sectarian divides within Lebanon resurface, and also old political divides,” Abdel Razzaq Takriti, a professor of history at Rice University who studies Arab radical movements, told Vox.

These tensions exploded in April 1975, when Christian nationalist militants attacked a bus carrying Palestinian fighters and their Lebanese comrades through a Christian Beirut suburb, killing 22 people.

And they were exacerbated by Israel, which meddled in the fighting in the hopes of pushing the PLO out of Lebanon and ensuring a friendly Maronite Christian government was in power. Israel directly supported the largest Maronite militia, the Phalange, providing arms, training, and funding, sometimes in coordination with the CIA. Israel also openly supported the leader of the Phalange movement for president, in the hopes that he would enter into a peace treaty.

Israel took a more direct role three years into the war: In March 1978, it invaded Lebanon in response to an attack by a Palestinian group that killed 34 Israelis. By the time Israeli forces withdrew later that month, as many as 2,000 Lebanese and Palestinians had been killed, 200,000 displaced, and dozens of villages in the south damaged.

It also helped turn the tide of the war. Before the invasion, combined left-wing Lebanese and Palestinian forces had made important gains. Israel’s attack, however, strengthened its relationship with the Maronite forces, which would continue through a second Israeli invasion in 1982.

The Lebanese Civil War was a deeply complex and devastating conflict; over the course of 15 years, around 100,000 Lebanese and Palestinians were killed, although some reports put that number as high as 150,000. The war finally ended in 1990, following the Taif agreement, which altered the balance of power within Lebanon’s government. But that resolution failed to address the war’s root causes, perpetuating the sectarian dynamics that still plague Lebanese society.

Israel was not the only outside country to become involved in Lebanon’s civil war; Syria, the US, and other Arab and European nations all contributed to the chaos. The civil war was happening in the context of the Cold War, and the US in particular was involved because it wanted to eliminate the possibility of communism (and Arab nationalism, which it saw as a corollary) from taking hold in the Middle East.

But Israel’s support of the Maronite sect — and particularly the bloodthirsty militia — only entrenched the unworkable status quo and showed disregard for the country’s sovereignty, fueling Lebanese and Palestinian distrust in Israel.

Israel invaded Lebanon again in 1982 to finally oust the Palestine Liberation Organization from the country following an offshoot organization’s assassination attempt on an Israeli politician. This time Israeli forces made it all the way to Beirut.

At this point, Israel was still financially and materially supporting the Christian Phalangist militia. In September, the Phalangist militia, with Israeli assistance, carried out a massacre on the Sabra and Shatila refugee camps in west Beirut, despite the fact that the PLO had already left Lebanon. As many as 3,500 Palestinian and Lebanese civilians were killed, and the incident provoked worldwide outrage.

Under pressure from the US and UN (in the form of a Security Council ceasefire resolution), Israeli forces moved back to the south following the massacre, ending up south of Lebanon’s Litani River. But Israel would continue to occupy southern Lebanon until 2000, both with ground troops and via its proxy militia there, the South Lebanon Army.

Southern Lebanon was — and still is — largely Shia, one of Lebanon’s historically disenfranchised religious sects. It is also mostly rural, economically disadvantaged, and physically removed from the center of power in Beirut. The southern Shia population had no protection from repeated Israeli invasions, since the Lebanese military presence there was an Israeli proxy force.

In the face of this, Hezbollah formed in southern Lebanon in 1982, offering southern Shia communities protection from Israel, stronger political representation in Beirut, and access to resources like health clinics and community centers. It grew into a well-equipped guerilla fighting force supported by Israel’s arch-foe, Iran — which means Israel sees Hezbollah as an existential threat along its northern border. Hezbollah’s early vow to destroy Israel only fueled this understanding.

Israel would launch two military operations against them — one in 1993 and one in 1999, before withdrawing from Lebanon in 2000.

In the new millennium, there came a shift in Israeli-Lebanese relations. With the PLO leaving Beirut in 1982, renouncing armed resistance as part of the Oslo Accords, and shifting to an administrative role in the Palestinian struggle, Israel’s focus has been on Hezbollah. And the scale of the conflict has shrunk, with most operations taking place on either side of the Israeli-Lebanese border.

The first significant attack of this new phase came in July 2006, when a Hezbollah unit crossed into Israeli territory, kidnapping two Israeli soldiers and killing eight while also firing a rocket barrage into northern Israel. That touched off a month of brutal, intense conflict including aerial bombardment on Lebanese territory. That conflict ended in a UN-backed ceasefire on August 14, 2006.

Since then, Hezbollah and Israel have often traded rocket fire over Lebanon’s southern border. In recent months, those attacks have intensified; following Hamas’s October 7, 2023, attack on Israel, Hezbollah has launched thousands of rockets into Israeli territory.

Israel has long had plans to take out Hezbollah, according to Natan Sachs, director of the Middle East program at the Brookings Institution. But it only began to act on those plans in recent weeks. Now, assassinations — particularly of military leader Fuad Shukr and of former Hezbollah head Hassan Nasrallah — have taken out significant portions of Hezbollah’s top- and mid-tier leadership. “Israel has been preparing for this for 18 years,” Sachs said.

Israel has managed to seriously damage Hezbollah by killing its leadership and destroying weapons supplies — but it’s unlikely the group will be permanently destroyed or impaired, something Israel has tacitly acknowledged. What’s more, this present invasion, coupled with the destruction and death Israel has wrought against Palestinians, has only served to fuel fresh outrage in Lebanon — and the world — over Israel’s actions.

Over the decades, Israel has tried, whether through military or political action, to shape Lebanon according to its interests. It’s repeatedly failed, with its actions sometimes helping to create new foes, as was the case with Hezbollah. Today Israel’s willingness to try to influence internal Lebanese politics seems to be no different: Israeli Prime Minister Benjamin Netanyahu has threatened to destroy the country unless it pushes Hezbollah out.

Thus far, however, this invasion, like military actions in the past, may only foment even more animosity toward Israel, and further destabilize Lebanon.