They fought rebels, militants including ISIS there, beat them, looks like they are back as the article references.
Philippines: scores of Islamic State fighters on Mindanao island
Carmela Fonbuena
The threat of Islamic State is mounting again in the Philippines, with estimates there could be between 40 to 100 foreign fighters, and a growing momentum among local pro-Islamic State militant groups.
In May last year, the Mindanao city of Marawi was overrun by Isis fighters and a caliphate declared. It took a bloody, five-month siege by the army, in which 1,200 lives were lost, for the government to regain control.
But one year on from Marawi’s liberation, Prof Rommel Banlaoi, chairman of the Philippine Institute for Peace, Violence and Terrorism Research, told the Guardian that he had seen records of up to 100 foreign fighters on the island – a combination of old and new arrivals since the Marawi siege last year – who want to re-establish the east Asia wilayah (or East Asia Isis province) crushed in the fighting.
Read more at: https://www.theguardian.com/world/2018/nov/11/philippines-scores-of-islamic-state-fighters-on-mindanao-island?CMP=share_btn_tw