In 2017 the black flag of the Islamic State group flew in the southern Philippines as a mixture of local and foreign fighters attacked the Islamic City of Marawi.

While the government did eventually regain control, it took five months to break the siege and many terrorist leaders escaped during the fighting. It's led to fears that the extremist violence could spread.

In this Inquiry we investigate the long history of conflict which provided a fertile place for IS's Islamist ideas to grow, and ask how important the region is to IS now that they're retreating in the Middle East.

(Image: Destroyed buildings in what was the main combat area in Marawi. Photo: Merlyn Manos/Getty Images)