Palestinian Islamic Jihad, the militant group the Israeli military is targeting in its latest bombardment of the Gaza Strip, is an Iran-backed organisation with a long history of attacks on Israel.
The founders — Fathi Shaqaqi, Abdul Aziz Odeh and Bashir Moussa — returned to Palestine after being expelled from Egypt following the assassination of Anwar Sadat in 1981. Shaqaqi had been arrested earlier by Egyptian authorities after writing a book in praise of Iran's 1979 Islamic Revolution and its leader, Ayatollah Ruhollah Khomeini.
After organising in the Israeli-occupied territories and elsewhere in the early 1980s, the group is believed to have carried out its first successful attack, the killing of an Israeli military police captain, in August 1987. This was a few months before the first Palestinian intifada, or uprising.
The following year, Israel expelled Shaqaqi and Odeh to Lebanon. While there, Shaqaqi developed ties with Iran's Islamic Revolutionary Guard Corps and Lebanon's Iran-backed Hezbollah movement.
Designated as a terrorist organisation by the US and EU among others, Islamic Jihad is regarded as a sister organisation to Hamas, the Islamists who have controlled Gaza since 2007. Both were born out of the Muslim Brotherhood, the Islamist movement that was established in Egypt in the last century, and are supported by Iran.
Islamic Jihad formed its armed wing, known as the Al Quds Brigade, in 1992. Working in co-ordination the military wing of Hamas, the Ezzedine Al Qassam Brigades, it carried out a string of suicide bombings against Israeli targets in the 1990s in an attempt to derail the Oslo peace accords.
The group also claimed responsibility for many suicide bombings during the second Palestinian intifada from 2000 to 2005.
Among the deadliest attacks carried out by Islamic Jihad were the double suicide bombing of a military bus stop at Beit Lid near Netanya on January 22, 1995, which killed 19 and injured 69; the suicide bombing of a Tel Aviv shopping mall on March 4, 1996, which killed 20 and injured 75; the car bombing of a bus near Afula on June 5, 2002, which killed 17 people and injured 38; and the August 19, 2003 suicide bombing of a bus in Jerusalem which killed 21 people and injured more than 100.
Shaqaqi was assassinated by Israeli agents in Malta in 1995. Its current leader Ziad Al Nakhalah, was appointed after Israel assassinated his predecessor Baha Abu Al Ata in 2019.
Although primarily based in Gaza, Islamic Jihad also has a strong presence in the Israeli-occupied West Bank, particularly in the northern city of Jenin. Many of the group's senior leaders have been based in Damascus.
Israel insists the group's ties with Iran have deepened.
Prime Minister Yair Lapid said that Al Nakhalah was in Iran when he authorised "pre-emptive" strikes against the group on Friday, citing the threat of attacks.
"The head of Islamic Jihad is in Tehran as we speak," Mr Lapid said, just hours after Israeli jets killed Tayseer Al Jabari, one of the group's senior military leaders in Gaza.
Maj Gen Hossein Salami, the head of Iran's Revolutionary Guards, told Al Nakhalah on Saturday during a meeting in Tehran: "We are with you on this path until the end."
The Israeli military claim Islamic Jihad has a rocket arsenal comparable in size to that of Hamas, which was able to field an estimated 7,000 rockets during last year's war in Gaza. Analysts say the group's rockets have a shorter range however.
Although Islamic Jihad regularly operates in co-ordination with Hamas, notably during the 11-day war with Israel last May, the continuing conflict further highlights its independence.
Hamas has not fired rockets at Israel since the exchange of fire began on Friday.
In 2019, Hamas sat out fighting between Israel and Islamic Jihad that was triggered by the assassination Al Ata.
And whereas Hamas leaders have made statements softening their commitment to the destruction of Israel, the smaller organisation has made no such move and rejects any compromise.