The raids by the Egyptian air force on Islamic State (IS) camps and arsenals is an escalation in Cairo's 20-month campaign against the cult. The strikes were in retaliation for the murder by mass beheading of 21 Egyptian Coptic workers held hostage by IS in Libya.
The air action coincided with Egypt’s shift from a defensive to an offensive strategy for containing and ultimately defeating IS in northern Sinai.
Last November, Sinai-based Ansar Beit al-Maqdis (ABM) declared allegiance to IS and rebranded itself the Sinai Province of Islamic State, stretching from Raqqa in north-central Syria to Mosul in northern Iraq.
ABM emerged in 2012, following the toppling of Egypt's president of 30 years, Hosni Mubarak. The group repeatedly blew up a pipeline exporting Egyptian natural gas to Israel and Jordan, fired rockets at the Israeli port of Eilat and attacked an Israeli border patrol following a US-made film seen by some Muslims as insulting the Prophet Muhammad.
During the year-long presidency of Mohamed Morsi, a Muslim Brotherhood veteran, ABM recruits and weapons poured into Sinai, largely from war-torn Libya, establishing a strong connection between Sinai and Libyan radicals.
Reluctant to alienate the brotherhood, ABM kept a relatively low profile while Morsi was in office. After he was ousted in July 2013 it stepped up attacks on troops, police and civilians in North Sinai, South Sinai and Egypt "proper".
In August 2014, Ansar fighters beheaded four soldiers, in imitation of IS treatment of captives in Syria and Iraq. That October, ABM killed 30 soldiers in the most deadly attack on the Egyptian army in decades. Last month, Sinai Province killed 27. For the Egyptian military this was the last straw.
Cairo appears to be tackling IS on its own although it enjoys the support of one faction in Libya, which sent combat aircraft into action alongside Egypt’s F-16s. Egypt is also backed by the United Arab Emirates, Saudi Arabia and other members of the US-led coalition fighting IS in Syria and Iraq.
Egypt’s situation is quite different to that of Syria and Iraq, where IS holds central towns and wide swathes of territory. IS’s Sinai base is a small, distant and neglected province.
Since IS won victories on the battlefield, the cult has become fashionable, winning many recruits. It has taken root across Libya and in Algeria and Yemen and is deeply embedded in Turkey.
Due to sophisticated campaigns on social media and effective networks in Europe, IS has also attracted the majority of the 2,500-3,000 European jihadis deployed in Iraq and Syria. IS recruits returning home to Europe or remaining there as “sleepers” are considered serious threats.
IS recruitment is promoted in prisons. Omar Abdel Hamid al-Hussein, who carried out the Copenhagen killings on Saturday, did so two weeks after he left prison, where he had served time for attempted murder. Two of the men involved in last month's French attacks, Cherif Kouachi and Amedy Coulibaly, met in prison.
Coulibaly claimed for IS his murder of a policewoman and four customers at a kosher shop while Kouachi and his brother Said, who murdered 12 people at Charlie Hebdo magazine, said they belonged to al-Qaeda in the Arabian Peninsula, based in Yemen, an IS rival.
IS has been successful partly because it was ignored until it captured Mosul, Iraq’s second city, last June, ringing alarm bells in western and Arab capitals. It had been getting funds and arms from Qatar, Saudi Arabia and Kuwait while Turkey funnelled weapons and fighters into Syria and Iraq.
Since then, IS has been designated a terrorist organisation by the United Nations and western and Arab governments, and the UN security council is – belatedly – poised to bar IS funding.