The viciously militant Islamic State has found another adherent in the form of Egypt's most dangerous militant group, Ansar Beit al-Maqdis.
The group has slaughtered hundreds of Egyptian soldiers and police officers, recruited experienced fighters and staged increasingly sophisticated raids from the western desert of Africa to the Sinai Peninsula. They have beheaded informants and killed an American in a carjacking, say Western officials familiar with intelligence reports.
On Monday Ansar Beit al-Maqdis pledged obedience to the organisation that calls itself the Islamic State, becoming its first significant international affiliate – perhaps in the hope that the IS link will provide new money, weapons and recruits to battle the government in Cairo.
The affiliation could pull the Maqdis group away from its current, almost exclusive focus on attacking Egyptian military and security forces toward the Islamic State's indiscriminate mass killings of civilians, apart from ruining the country's already fragile economy, heavily dependent on tourist dollars.
The decision injects the Islamic State into the most populous and historically most influential Arab nation, weeks into an American-led bombing campaign against IS strongholds in Syria and Iraq.
The endorsement is also seen as a major victory for the Islamic State in its rivalry with Al Qaeda - a group with deep Egyptian roots - and could now help recruit fighters and affiliates far beyond Egypt.
The link is also the latest manifestation of a swirling descent into violence around the region amid the dashed hopes for democracy of the Arab Spring uprisings three years ago.
In immediate terms, the Islamic State could share from its wealth of looted money and oil, seized-weapons stores or jihadi prestige to add new fuel to the Egyptian group's insurgency at a critical turning point.
In recent weeks, Ansar Beit al-Maqdis has come under a crackdown by the Egyptian military, which has begun the evacuation and destruction of hundreds of homes in an attempt to eradicate the group from its havens in northern Sinai. But the group has confounded the confident predictions of Egyptian officials that it would soon be defeated, raising fears that the fight may just be beginning.
Having killed hundreds of soldiers and police officers in a rampage of violent retaliation for the military ouster of the Islamist president last year, Ansar Beit al-Maqdis has more recently carried out a handful of increasingly sophisticated and deadly attacks on military camps at both the eastern and western extremes of the country, according to Western officials and analysts.
An attack in the Western desert on 19 July killed at least 21 soldiers, and another on 24 October in Sinai killed at least 31 - both strikes demonstrating that Ansar Beit al-Maqdis has now recruited more skilled and experienced fighters.
Most alarmingly for the Egyptian military, Egyptian leaders believe the group has developed military informants with inside information about army deployments.