( CNN ) -- In the many media stories about the Islamic State of Iraq and Syria , much of the focus has rightly been on the thousands of foreign fighters ISIS has attracted , its brutal tactics and its robust social media presence . But an arguably even more important development has not received the attention it deserves : the group 's widening influence across the Muslim world , driven by the numerous terrorist and insurgent organizations that have recently sworn loyalty to it . In the past six months , ISIS has drawn into its fold some dozen groups from Algeria to Pakistan . Al Qaeda , in contrast , had been in existence for a decade before it recruited its first affiliate , Egypt 's Jihad Group , in 1998 . And , in its 2Â½-decade existence , al Qaeda has only manged to add some half dozen affiliates , one of which was al Qaeda in Iraq , the parent organization of ISIS that has now split off from the core al Qaeda organization . Indeed , just this week , an ISIS delegation met with leaders of a splinter group of the Pakistani Taliban to talk about how to unify Pakistani militants , The Associated Press reported . Also this month , Ansar Beit al-Maqdis , one of the most violent militant groups in Egypt , pledged allegiance to ISIS , The New York Times reported . ABM is believed to have been responsible for an attack on a police checkpoint near Gaza last month that killed 30 Egyptian soldiers . And ISIS has continued to expand its geographical reach . Three other groups -- al-Mujahidin in the Arabian Peninsula , al-Mujahidin in Libya and al-Mujahidin in Yemen -- also recorded statements of allegiance to ISIS in November , which ISIS broadcast online . Meanwhile , ISIS now controls the eastern Libyan city of Derna , not far from the Egyptian border . And last month , six Pakistani Taliban leaders reportedly swore allegiance to ISIS in an audio message , although Shahidullah Shahid , the Pakistani Taliban 's official spokesman , said he was speaking for himself and five other Taliban leaders in the message , not for the rest of the Pakistani Taliban . The Taliban reacted by firing Shahid , but a senior Taliban official told the BBC that `` he was the most important of the five who have left us '' and said that the leaders had defected because they were unhappy with senior Taliban leaders . Among other groups that have pledged allegiance to ISIS is Jund al-Khalifa ( Soldiers of the Caliphate ) , a terrorist group operating in Algeria . Previously , the group was part of al Qaeda 's North African branch , al Qaeda in the Islamic Maghreb , until the group split from AQIM because it was `` deviating from the true path . '' And just 10 days after proclaiming its allegiance to ISIS , Jund al-Khalifa beheaded Herve Gourdel , a 55-year-old French hiker they had taken hostage . ( Beheading Western hostages is , of course , one of ISIS ' signature tactics ) . Inside Syria and Iraq , ISIS has also gathered up smaller militant groups . For example , Ansar al-Islam , a former al Qaeda-linked group , is now cooperating with ISIS . Also , Jaysh Mohammed ( Army of Mohammed ) used to work to repel U.S. forces from Iraq and has now joined the ranks of ISIS . Finally , ISIS and the al Qaeda-aligned Nusra Front had previously been at war with each other in Syria for much of this past year . But this month , representatives from the two groups met in Syria and agreed to stop fighting each other and focus on fighting their common enemies , sources told The Associated Press . This brings together the two most effective Sunni militant groups fighting in Syria . Why are all of these militant groups suddenly pledging their allegiance to ISIS or aligning themselves with the group , and in many cases giving up former affiliations with al Qaeda 's core group to do so ? The answer is simple : ISIS is successful . In many ways it really is the `` Islamic State of Iraq and Syria '' that it claims to be , because it has taken large portions of both countries from government control , replacing local administrators with ISIS governors who distribute social services . ISIS is also winning critical cities and key points of infrastructure , including dams and oil wells , and that means the group has substantial funding and resources at its disposal . Partnering with ISIS makes sense from an economic perspective for many of these organizations , especially the smaller militant groups operating inside Syria and Iraq . For other militant groups around the Muslim world , it allows for a cross-pollination of ideas and training through a sort of jihadist exchange program , where some groups send members into Syria or Iraq to learn from ISIS . ISIS controls territory in a 400-mile swath from Aleppo in the west of Syria to Fallujah in the east , near the Iraqi capital , Baghdad , while its dozen or so affiliated organizations stretch from the coast of North Africa to the mountains of the Hindu Kush . The fact is that al Qaeda 's core organization can only dream of such success .
David Bergen : More and more terrorist and insurgent groups are swearing loyalty to IS . In past six months , IS has recruited about a dozen groups , he says . IS ' perceived success is attracting these groups , Bergen says .