Who is Mohammed Deif, Hamas military chief, whom Israel killed in air strike?

The Israeli military declared on Thursday that they had struck and killed Mohammed Deif, the military chief of Hamas, on July 13 in the Khan Younis area of southern Gaza. Deif, 58, was thought to be the mastermind behind Hamas' October 7 attack, which resulted in the murder of 39,445 Palestinians—including over 15,000 children—and the injuries of over 91,073 others by Israel as of July 31, according to Al Jazeera.

Al Jazeera reported that an official told news agency AFP that Deif is in good health and is supervising Hamas' operations, despite Israel's claims to have proof of his death.

Deif was born in 1965 in one of Khan Younis' refugee camps. His birth name was Mohammed Diab Ibrahim al-Masri. Deif managed to earn a degree in science from the Islamic University of Gaza, where he studied physics, chemistry, and biology, despite coming from a low-income family and growing up in one of the few camps for refugees that Israel established after 1948. In addition, Deif served as the university's president and staged comedies.

Deif participated in the first intifada, or the Palestinian uprising, which started in 1987 and ended in 1993 with the signing of the Oslo Accords, having joined Hamas at the time of its founding in 1987. At the height of the intifada in 1989, Deif spent sixteen months in Israeli detention.
 
After Israel killed Salah Shehadeh, the Qassam Brigades' founder and predecessor, in 2002, Deif assumed command of the organisation. According to Al Jazeera, on October 7, attacks inside Israel were carried out by the military wing of Hamas, the Qassam Brigades, which resulted in the deaths of over 1,400 people and the kidnapping of approximately 200 others.