Israel’s Shin Bet domestic intelligence agency confirmed it targeted Jaabari in a joint strike with the army, charging he had been “directly responsible for executing terror attacks”.
Jaabari deliberately kept a low profile, was rarely photographed and avoided being interviewed.
But a deal to secure the release of Israeli soldier Gilad Shalit brought him out of the shadows last year.
He allowed himself to be caught on camera on 18 October, 2011 as he delivered Shalit to Egypt as part of a key prisoner exchange deal with the Jewish state.
Jaabari hailed from a respected activist family in the Shejaiya neighbourhood of Gaza City, with close ally Abu Hudaifa describing him as confident in his own decisions and committed to following up personally on issues.
A history graduate from Gaza’s Islamic University, Jaabari was arrested by Israel in 1982 when he was an activist with Fatah, the secular Palestinian national movement which has long been a bitter rival of Hamas.
It was in prison, where he spent 13 for planning deadly attacks, where he met some of Hamas’s top leaders such as Abdel Aziz al-Rantisi, Ismail Abu Shanab, Nizar Rayyan and Salah Shehadeh and decided to join the movement.
Shehadeh led the Ezzedine Al-Qassam Brigades until he was killed in a massive Israeli air strike in July 2002, after which he was replaced by Mohammed Deif.
Several months later, Deif was badly wounded in another Israeli strike and went underground, leaving Jaabari as the operational head of the armed movement at the height of the second intifada, or Palestinian uprising.
Known in Gaza as “the general” or the “chief of staff,” Jaabari could occasionally be spotted walking alone in the street.
But, as one of the top names on Israel’s most wanted list, Jaabari took almost obsessive care when it came to his personal security.
Jaabari had previously been the apparent target of more than one Israeli assassination attempt, including a 2004 air strike that killed his eldest son Mohammed, along with his brother and several of his cousins.
He was also targeted by the Palestinian security forces, who arrested him in 1998 and held him for nearly two years on account of his activities with Shehadeh and Deif.
After Jaabari took over the day-to-day running of operations, the armed group became increasingly professional.
He was also credited with playing a leading role in the Islamist movement’s takeover of Gaza in summer 2007, which saw its militants expelling Fatah forces after a week of bloody fighting and a botched coup attempt by Fatah against a democratically elected Hamas.
In addition to his leadership role in Ezzedine Al-Qassam, Jaabari was a member of the movement’s political leadership and the founder of Nur, an association to help “martyrs and prisoners.”
He had two wives, including a daughter of his mentor, Shehadeh.