Having taken land five times the size of Lebanon, and establishing the first "caliphate" in nearly 100 years, the rapid advances of ISIS are dominating headlines around the world and instilling fear in many across the region.
When Iraq's second-biggest city fell to ISIS, White believes it wasn't a question of serious fighting, but that the mass desertions on the part of the Iraqi army allowed ISIS to take Mosul.
It's likely that Iraqi soldiers, lacking direct combat experience, may also have been intimidated by ISIS' presumed experience, with many members having already been in Syria for several years.
White doubted how much time spent in Syria had really benefited the ISIS insurgents now in Iraq.
When ISIS faced Kurdish peshmerga forces in the north, ISIS weaknesses became apparent.
Shiraz Maher, senior fellow at the International Centre for the Study of Radicalization, King's College London, thinks that Abu Bakr al-Baghdadi, self-styled caliph of ISIS, has been very clever in his approach so far, with ISIS commanders leading the battles, and local Sunni tribesmen doing the actual fighting.
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