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Israel’s retaliation with the stated aim of "wiping out" Hamas has left a trail of devastation, killing at least 11,000 Palestinians.
But while Hamas makes headlines, the group has at least 11 local allies fighting alongside it.
The most well known of these is Palestinian Islamic Jihad – formed with Iranian backing in 1981, six years before Hamas, which emerged out of the Muslim Brotherhood.
Both PIJ and Hamas, through their military wings the Al Quds Brigades and Al Qassam Brigades respectively, are now well equipped with Iranian weapons, having also received military advice from Tehran.
Hamas is by far the strongest group, with anywhere between 25,000 and 40,000 fighters, but some of their junior partners are considered more militant, particularly the PIJ.
Joint Operations Room
Since 2018, factions have co-ordinated through a Joint Operations Room that brings together groups with varying influences.
These range from Islamist groups such as Hamas and PIJ to the Marxist Popular Front for the Liberation of Palestine and its militant wing, the Abu Ali Mustafa Brigades. They include one of Hamas's rivals, the Al Aqsa Martyrs' Brigades, previously linked to Fatah, the dominant faction in the Palestinian Authority.
"Each of the Palestinian factions has its own history: a historical context in which it was born, mentors and an ideological project for building the Palestine of tomorrow: nationalist, Marxist, Islamist," said Pierre Boussel, associate fellow at France's Fondation pour la Recherche Strategique.
Despite tactical differences, the Joint Operations Room is an attempt to bring these factions together, for what Mr Boussel described as "their shared goal of creating a Palestinian state with Jerusalem as its capital."
Hamas usually leads the operation, although sometimes PIJ takes a leading role, said Jordanian political commentator Hazem Ayyad.
As for the smaller factions, "Aqsa Martyrs' Brigades and Abu Ali Mustafa Brigades have similar weight in the Joint Operations Room, less for the Democratic Front,” Mr Ayyad told The National.
Militants from different backgrounds also co-ordinate through Popular Resistance Committees and its armed wing, the Al Nasser Al Salah al din Brigades, comprised of former members of Al Aqsa Martyrs' Brigades and the PFLP who co-ordinate closely with Hamas.
Here are some of the main groups currently fighting against Israeli forces in Gaza.
Palestinian Islamic Jihad
PIJ and its armed wing the Al Quds Brigades is seen as more directly an Iranian proxy group than Hamas, which has links to Tehran but has broken with it on key issues.
The war in Syria highlighted this difference. PIJ maintained ties with Iran's ally the Syrian regime throughout the war, while Hamas closed its office in Damascus between 2012 and 2022 in opposition to President Bashar Al Assad’s violent crackdown on rebel groups.
PIJ led operations in the August 2022 Gaza war, firing about 1,000 rockets from its arsenal over several days of fighting.
Those weapons were thought by some analysts to rival Hamas’s own rocket arsenal, including long-range rockets capable of hitting Israeli cities 120km from Gaza.
According to Mr Ayyad, PIJ has “its own military and political decision making independent of Hamas, but at the same time is more dependent on Iran and does not have as deep roots in Gaza as Hamas".
"Lately almost everyone has been gravitating towards Hamas, even the leftists," he says.
Al Aqsa Martyrs' Brigades
The group is a coalition of militias linked to Fatah, the dominant faction in the Palestinian Authority, which rules the occupied West Bank.
The brigades emerged in the early 2000s in the Second Intifada, the bloody uprising against Israeli occupation.
While it claims to be fighting in Gaza alongside Hamas, its historic base of operations is the occupied West Bank, and it has a turbulent relationship with Hamas.
The group has been accused of receiving covert funding from Fatah, as well as playing a role on their governing council.
Fatah fought a war against Hamas in 2006-2007, in which some of the brigades' members were said to have fought on the side of Fatah. One of their commanders, Samih Al Madhoun, was allegedly assassinated by Hamas’s Al Qassam Brigades in the Nuseirat refugee camp.
Around that time, according to a report by the Council on Foreign Relations, the Palestinian Authority decided to rein in the Al Aqsa Martyrs' Brigades' activities, arresting several of its commanders.
Popular Front for the Liberation of Palestine
The Marxist group was formed in the late 1960s by George Habash, a former doctor whose sister was killed during the 1948 Arab-Israeli war.
It military wing, the Abu Ali Mustafa Brigades, named its armed wing after Abu Ali Mustafa, Habash’s successor, who was assassinated in 2001.
Formerly a part of the Palestinian Liberation Organisation, the hardline nationalist and socialist group made world headlines in 1976 when it hijacked an Air France jet with 248 passengers on board, mostly Israelis, and flew it to Entebbe in Uganda.
Israeli commandos later rescued all but three of the hostages, losing one commando in the process, Yoni Netanyahu – Israeli Prime Minister Benjamin Netanyahu’s brother.
The hijacking was joined by German communist terrorist group the Revolutionary Cells, a similar group to the Red Army Faction, better known as the Baader–Meinhof Group, who also worked with PFLP.
At the time, the PFLP sought backing from Communist states, but enjoyed limited success in this goal and spent years in the political wilderness after the collapse of the Soviet Union in 1991.
Ahmed Saadat, the group’s political leader, and two of his colleagues enjoyed electoral success in the 2006 Palestinian elections, but the group has struggled to obtain a leading position among anti-Israeli groups.
The PFLP splintered shortly after its founding, with the PLFP-General Command forming in opposition to the Marxist origins of the group. The latter backed President Bashar Al Assad during the Syrian civil war, when the Syrian Palestinian community became divided over support for Damascus and an almost nationwide revolt.
“The PFLP-GC appears to me more active in Syria now, and may have participated in sporadic recent rocket attacks against Israeli targets in the Golan,” Mr Ayyad says.
The proliferation of so many factions could complicate efforts to stabilise Gaza after the war, experts say.
“There is certainly the possibility that Gaza will fracture politically. Assuming the Israelis are successful, Hamas – as an organisation – will be shattered,” says Raphael Cohen, an expert on the war in Gaza with the US Rand think tank.
“But the Palestinian Authority already struggles with legitimacy. And then there are the smaller groups already in Gaza (PIJ, for example). I can also imagine new groups springing up, especially if the operation leaves a power vacuum,” he says.
“All in all, it’s not going to be as simple as turning over the keys to a Palestinian group once the operation is over. It’s going to be far messier, unfortunately.”