What-so-called Islamic State in Iraq and Syria (ISIS) has controlled al-Musel city northernern Iraq, while Iraqi forces were fled amid sudden and strong cotralateral attack.
Since months ago, ISIS partly controlled al-Ramadi district, but government forces alongside armed loyal forces called "al-Sahwat" -- the later was originally founded by Americans during direct Iraq's invasion to face al-Qaeda groups-- regained control again and cheased ISIS members, however, al-Qaeda affiliated group (ISIS) raided local University Campus few days ago.
A worthy question rises here: What does make ISIS strong enough to attack many regions in Iraq and Syria?
Although regional and international governments have declared unmreciful war against al-Qaeda and its local branches, they become stronger and control more areas in Syria and Iraq.
Undoubtedly, ISIS has become the strongest anti-goverment forces in Syria; they control most of Eastern and North Eastern Syrian districts, particularly, Deir Ez-Zour and Al-Raqqa respectively.
After al-Musel of Iraq was raided by ISIS, Turkish consultant and nearly ninety Turkish citizens became hostages between ISIS's hands, thereafter Turkey immediately called NATO to meet, in order to discuss the situation.
Contradictory, officially-backed terrorism, and local culture are feeding terrorism
While Western and pro-Western Arab government decided to topple down Bashar Al-Assad regardless of costs, they found themselves dealing with terrorist groups such as An-Nusra Front and ISIS against Syrian regime, meanwhile, the same terrorists -- they are also classified as terrorist organizations in the EU and US-- are not allowed to attack American-designed Iraqi regime to maintain oil flow toward Western companies, especially after the American troops withdrew from Iraq. So the Western governments indirectly supported ISIS in Syria, hopefully, they will not move to neighboring Iraq.
Notably, terrorist organizations rise up in eccentric areas inhabited by least educated populations. Demonstrating al-Qaeda foci; one can see their geographic distribution world widely as following:
Sinai of Egypt, Pakistan's far borders (eastern), Syria's Al-Raqqa and Deir Ez-Zour, African Sub-Sahara (Parts of Mali, Algeria and Tchad), Somalia and middle Yemeni desert (Shabwa and Ma'reb).
Moreover, al-Qaeda and its local branches are absolutely supported by intelligence agency(ies), at least, by making blind eyes on their financial and arming support.