Al-Arouri was killed in a drone strike on a Beirut neighbourhood that is a stronghold of the Lebanese group Hezbollah, allies of Hamas. The Hamas leader had been in Lebanon since 2015 – one of tens of thousands of Palestinians in the country.

Successive waves of Palestinian refugees to Lebanon have led to a stateless population of up to about 270,000 people, who live in 12 camps across the nation.

It started with the Nakba of 1948, when 750,000 Palestinians were expelled from Palestine during the creation of Israel, and has continued since, as resistance leaders and refugees alike sought shelter from Israeli attacks.

But while Lebanon has hosted these refugees, they have faced systemic discrimination – and the Palestinian community and its leaders have constantly lived under the threat of Israeli attacks.

Who governs the Palestinian camps?

Since 1969, Lebanese security forces have been banned from entering the camps, with security provided by several armed Palestinian factions.

At times, these armed groups have clashed among themselves, vying for influence, control and support from the Palestinian community.

The refugee camps remain recruitment grounds for Palestinian armed factions: in early December Hamas put out a call for people in the camps to join the group.

How many refugees are there?

Accurate population numbers are hard to come by, with the 2017 Lebanese census reporting about 170,000 refugees resident within the Lebanese camps, while the UNRWA – the UN agency which supports Palestinian refugees – reports more than 270,000 Palestinians live in Lebanon.

But as many as 475,000 Palestinians are registered with UNRWA in Lebanon.

What are conditions like?

Overcrowding, poverty and a lack of jobs characterise the camps.

Most Palestinians are precluded from obtaining the identity cards needed to access most jobs or social services. Instead, as Lebanon seeks to preserve its own fragile sectarian balance, they must rely upon the UNRWA to provide them with many of the necessities of daily life.

How old are these camps?

Palestinians first arrived in Lebanon in significant numbers in 1948 following the creation of Israel.

Initial numbers have since been bolstered by further arrivals following the 1967 Arab-Israeli war, which resulted in Israel occupying further stretches of Palestinian territory. More recently have come from those fleeing the fighting in Syria.

Have they always served as bases for Palestinian armed groups?

In the late 1960s, the Palestinian Liberation Organization (PLO) was fighting against Israel on several fronts. Principally, it operated out of Jordan, where about two million refugees were registered, and Lebanon, where poor conditions, non-existent infrastructure and substandard accommodation helped spread a sense of injustice.

How influential was the PLO in Lebanon?

Following a series of clashes between the Lebanese military and heavily armed Palestinian militias in 1968 and 1969, the Lebanese military signed an agreement known as the Cairo Accord.

While the details were closely guarded, the accord granted the Palestinians autonomy over the camps’ administration as well as the right to continue the armed struggle from Lebanon.

Shortly after the agreement was signed, the PLO was expelled from Jordan, where it had helped stage a revolt against the king, to the Lebanese camps where it enjoyed greater freedom to operate.

Through the 1970s, leaders of the PLO and its factions based in Lebanon were repeated targets of Israeli assassination attempts.

How deeply did its influence reach?

In 1982, the organisation was ejected from Lebanon to Tunisia, following its participation in the Lebanese civil war.

However, during its time in Lebanon, the group had drawn upon dissatisfaction within the refugee camps to establish significant control over southern Lebanon, including founding its own police force, before the region was subsequently occupied by Israel some years after the PLO’s departure.

How does that legacy manifest itself today?

A variety of groups now compete for control over the camps, and have a political and military presence in Lebanon.

Al-Arouri was a key interlocutor for Hamas with Hezbollah and other allied armed groups. At least two other senior Hamas military leaders were killed with him in the January 2 attack: Azzam al-Aqra, a leading commander of the Qassam Brigades – Hamas’s armed unit – outside Gaza; and Samir Fendi, the southern Lebanon commander for the Qassam Brigades.