They gave 24 hours for France to comply or face the hostage being decapitated. What happened next the world already knows.
But who is this group? The group is led by Abdelmalek Gouri, who before his defection was a regional leader of al Qaeda in the Islamic Maghreb (AQIM). According to twitter user @0101Muslim (who is now suspended), the group said "we have discovered the deviation in the path of al Qaeda mother organization and in the lands of the Islamic Maghreb". They then say, "we have previously disavowed their approach and allegiance to the caliph of the Muslims Sheikh Al-Baghdadi al-Qurashi". The statement goes on to reiterate that they have previously swore bayah (allegience) to al Baghdadi by saying, "we renew our allegiance and say to the conqueror Caliph and courageous hero Abu-Bakr al-Husayni al-Qurashi".
When the group first announced their creation on September 14th, the media went into a blaze reporting on a "new IS group in northern Africa". But according to the statement attributed to the group, they had already pledged their allegiance. Just days before, al Monitor reported that intelligence officials have tracked AQIM defectors to IS since "mid-August". While it is unclear that those who defected in mid-August are now in Jund al Khalifa, but it shows that defections from AQIM to IS were happening at least a month before this new group.
But AQIM is no stranger to breakaway factions. The biggest breakaway from AQIM before this was Mokhtar Belmokhtar (MBM), who left the group over disputes with Abdelmalek Droukdel, the emir of AQIM. Subsequently, MBM formed his own group, al-Mua'qi'oon Biddam (Those Who Sign in Blood Brigade). Al-Mua'qi'oon Biddam formally merged with the Malian Movement for Unity and Jihad in West Africa (MUJAO)--another AQIM splinter--in 2012, with MBM remaining a commander but ceding leadership to another veteran jihadist. His new group, al-Mulathamoon Brigade, is a designated terrorist organization by the US government. It is also worth noting that MBM has sworn allegiance to Aymen al Zawahri and al Qaeda--not the Islamic State like al Jazeera has reported--and is said to take orders directly from the senior leadership.
It is also worth noting that AQIM in Algeria has been rather inactive recently. In April of this year, AQIM killed 14 Algerian soldiers in Tizi Ouzou in an attack the BBC described as "one of the deadliest attacks on the Algerian military for several years." Before that was the In Ameneas hostage crisis in which MBM's group took hundreds of people hostage. But, AQIM seems to be more focused on the Sahel (i.e Mali, Niger, Chad, Mauritania), as well as establishing a foothold in Libya. A group that is focused on Algeria could potentially provide for more instability in the region.
It is also unclear just how big this group is. All in all, it obviously depends on how many people defected from AQIM and how many people they can recruit. Twitter user @maliwitness, a twitter analyst who specializes in North African and Sahelian jihadist groups, says that Jund al Khalifa appears to be relatively small and may have no more than 50 fighters. Taking into consideration that most of AQIM's leaders in Algeria are still loyal to AQ, it is unclear, as of right now, how successful this group will be.
Regardless, this still signals that the Islamic State is able to attract defections, albeit mostly small, from other parts of the world. It is also revealing that just hours before Jund al Khalifa kidnapped the Frenchman, IS spokesman Abu Muhammad al Adnani issued a statement calling for their supporters to kill citizens of those states taking part in the coalition against them.
It should be stated that the majority of defections from al Qaeda to the Islamic State have been small scale or from mid to low level commanders. All the senior leaders in the various branches of the international network appears to be remaining loyal to Zawahri. Of the groups in al Qaeda's "sphere of influence", it appears Abu Sayyaf in the Philippines is the only one that made a complete defection.
Jund al Khalifa, while small, is still significant as it shows that jihadists are still active in Algeria, including the northern part (most of AQIM in Algeria operations are in the south). It is not clear just how big of ramifications their creation brings for Algeria, but it will probably be very difficult for them to perpetrate large-scale terrorist attacks as the Algerian military has been pretty successful at keeping jihadist groups down in recent years. However, the threat of more kidnappings obviously remains.